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Pure Kotlin Devoxx PL 2021
- 1. DEVOXX PL 2021 DEVOXX PL 2021 DEVOXX PL 2021 PURE KOTLIN PURE KOTLIN PURE KOTLIN
- 3. Jarek Ratajski Jarek Ratajski Jarek Ratajski working for working for working for Digital Asset Digital Asset Digital Asset This talk does not represent company views, it This talk does not represent company views, it This talk does not represent company views, it is based on personal experience is based on personal experience is based on personal experience and opinions and opinions and opinions
- 7. AGENDA AGENDA AGENDA Propaganda The road to purity How to stay pure
- 8. AGENDA AGENDA AGENDA Propaganda The road to purity How to stay pure Links, frameworks, examples, disasters
- 9. PART 1 PART 1 PART 1 FP FP FP
- 10. PART 1 PART 1 PART 1 FP FP FP FUNCTIONAL PROPAGANDA
- 11. PART 1 PART 1 PART 1 FP FP FP FUNCTIONAL PROPAGANDA also known as also known as also known as Functional Programming Functional Programming Functional Programming
- 13. FP PROMISES
- 15. FP PROMISES less errors less code
- 16. FP PROMISES less errors less code less tests
- 17. FP PROMISES less errors less code less tests LESS != Nil LESS != Nil LESS != Nil
- 18. Two hours after deployment Two hours after deployment Two hours after deployment
- 19. What is functional programming? What is functional programming? What is functional programming? Programming with functions: Programming with functions: Programming with functions: deterministic total pure
- 20. What is functional programming? What is functional programming? What is functional programming? Programming with functions: Programming with functions: Programming with functions: deterministic total pure Ok, I have no idea. Just copied this definition Ok, I have no idea. Just copied this definition Ok, I have no idea. Just copied this definition from John De Goes ;-) from John De Goes ;-) from John De Goes ;-)
- 21. DETERMINISTIC depend on arguments only always yield same results for the same arguments fun fun fun hello() = "Hello Devoxx Poland" fun fun fun fact(n:Int) = if if if (n<=1) 1 else else else n*fact(n-1) fun fun fun radom() = Math.random()*0.7
- 22. TOTAL: Yields result/finishes for all possible arguments Yields result/finishes for all possible arguments Yields result/finishes for all possible arguments fun fun fun negate(a:Int):Int = -a fun fun fun radomize(v:String) = "Radom znowu $v" fun fun fun parseInt(t:String):Int = /* whatever */
- 23. PURE: Leaves no traces. Leaves no traces. Leaves no traces. The only (practical) way to The only (practical) way to The only (practical) way to detect if the function was called is by reading a detect if the function was called is by reading a detect if the function was called is by reading a result. result. result. fun fun fun add(a:Int, b:Int) = a+b [CODE A] val val val x = add(6,3) [OR] val val val x = 9 [CODE B]
- 24. fun fun fun add(a:Int, b:Int) = a*b //happy debugging fun fun fun add2(a:Int, b:Int) = run { Thread.sleep(a*1000) Thread.sleep(b*1000) return return return a+b } fun fun fun add3(a:Int, b:Int) = (a+b).also { log("was adding something...") }
- 25. Killer feature of functional programming Killer feature of functional programming Killer feature of functional programming
- 26. Killer feature of functional programming Killer feature of functional programming Killer feature of functional programming COMPOSABILITY COMPOSABILITY COMPOSABILITY
- 27. Killer feature of functional programming Killer feature of functional programming Killer feature of functional programming COMPOSABILITY COMPOSABILITY COMPOSABILITY
- 28. PART 2 PART 2 PART 2 KOTLIN PROPAGANDA KOTLIN PROPAGANDA KOTLIN PROPAGANDA
- 29. Kotlin killer feature? Kotlin killer feature? Kotlin killer feature?
- 30. Keyboard used by java developer Keyboard used by java developer Keyboard used by java developer
- 31. Kotlin Kotlin Kotlin == No more semicolons == No more semicolons == No more semicolons
- 32. Data class Data class Data class kotlin kotlin kotlin data data data class class class Person( val val val name:String, val val val age:Int, val val val drinking:Boolean = true )
- 33. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } }
- 34. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } } val drinking:Boolean = true val drinking:Boolean = true val drinking:Boolean = true
- 35. public public public final final final class class class Person { @NotNull private private private final final final String String String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String String String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String String String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String String String name, int int int age) { this this this(name, age, true);
- 36. public public public final final final class class class Person { @NotNull private private private final final final String String String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String String String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String String String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String String String name, int int int age) { this this this(name, age, true); equals and hashCode equals and hashCode equals and hashCode
- 37. public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this. return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } }
- 38. public public public int hashCode() { String var10000 = this this this.name; int var1 = ((var10000 != null ? var10000.hashCode() : 0) * 31 + this this this. return return return var1 + (drinking ? 1 : 0); } public public public boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true; } } return return return false; } else else else { return return return true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking }
- 39. Back to kotlin Back to kotlin Back to kotlin
- 40. fun fun fun main() = run { val val val p = Person("irek", 27, true) // }
- 41. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") }
- 42. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") println(p) //Person(name=irek, age=27, drinking=true) println(p1) //Person(name=Irek, age=27, drinking=true) }
- 43. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") val val val p2 = p1.copy(age = 28) }
- 44. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") val val val p2 = p1.copy(age = 28) val val val p3 = p2.copy(drinking = false) }
- 45. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") val val val p2 = p1.copy(age = 28) val val val p3 = p2.copy(drinking = false) val val val p4 = p3.copy(age = 29, drinking = true) } //Person(name=Zdzich, age=30, drinking=false)
- 46. fun fun fun main() = run { val val val p = Person("irek", 27, true) val val val p1 = p.copy(name = "Irek") val val val p2 = p1.copy(age = 28) val val val p3 = p2.copy(drinking = false) val val val p4 = p3.copy(age = 29, drinking = true) val val val p5 = p4.copy(name = "Zdzich", age = p4.age+1, drinking = false) println(p3) //Person(name=Irek, age=28, drinking=false) println(p5) //Person(name=Zdzich, age=30, drinking=false) }
- 47. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String name, int int int age) { this this this(name, age, true true true); } public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this.age) * 31; return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking=" + this this this.drinking + ")"; } @NotNull public public public final final final Person copy(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name");
- 48. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String name, int int int age) { this this this(name, age, true true true); } public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this.age) * 31; return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking=" + this this this.drinking + ")"; } @NotNull public public public final final final Person copy(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, this this this.drinking); } @NotNull public public public final final final Person copy(int int int age) { return return return new new new Person(this this this.name, age, this this this.drinking); }
- 49. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String name, int int int age) { this this this(name, age, true true true); } public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this.age) * 31; return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking=" + this this this.drinking + ")"; } @NotNull public public public final final final Person copy(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, this this this.drinking); } @NotNull public public public final final final Person copy(int int int age) { return return return new new new Person(this this this.name, age, this this this.drinking); } almost almost almost
- 50. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String name, int int int age) { this this this(name, age, true true true); } public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this.age) * 31; return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking=" + this this this.drinking + ")"; } @NotNull public public public final final final Person copy(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, this this this.drinking); } @NotNull public public public final final final Person copy(int int int age) { return return return new new new Person(this this this.name, age, this this this.drinking); } @NotNull public public public final final final Person copy(boolean boolean boolean drinking) { return return return new new new Person(this this this.name, this this this.age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name, int int int age) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, this this this.drinking); } @NotNull public public public final final final Person copy(@NotNull String name, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, drinking); } @NotNull
- 51. public public public final final final class class class Person { @NotNull private private private final final final String name; private private private final final final int int int age; private private private final final final boolean boolean boolean drinking; @NotNull public public public final final final String getName() { return return return this this this.name; } public public public final final final int int int getAge() { return return return this this this.age; } public public public final final final boolean boolean boolean getDrinking() { return return return this this this.drinking; } public public public Person(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); this this this.name = name; this this this.age = age; this this this.drinking = drinking; } public public public Person(@NotNull String name, int int int age) { this this this(name, age, true true true); } public public public int int int hashCode() { String var10000 = this this this.name; int int int var1 = ((var10000 != null null null ? var10000.hashCode() : 0) * 31 + this this this.age) * 31; return return return var1 + (drinking ? 1 : 0); } public public public boolean boolean boolean equals(@Nullable Object var1) { if if if (this this this != var1) { if if if (var1 instanceof instanceof instanceof Person) { Person var2 = (Person) var1; if if if (Intrinsics.areEqual(this this this.name, var2.name) && this this this.age == var2.age && this this this.drinking == var2.drinking) { return return return true true true; } } return return return false false false; } else else else { return return return true true true; } } @NotNull public public public String toString() { return return return "Person(name=" + this this this.name + ", age=" + this this this.age + ", drinking=" + this this this.drinking + ")"; } @NotNull public public public final final final Person copy(@NotNull String name, int int int age, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, this this this.drinking); } @NotNull public public public final final final Person copy(int int int age) { return return return new new new Person(this this this.name, age, this this this.drinking); } @NotNull public public public final final final Person copy(boolean boolean boolean drinking) { return return return new new new Person(this this this.name, this this this.age, drinking); } @NotNull public public public final final final Person copy(@NotNull String name, int int int age) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, age, this this this.drinking); } @NotNull public public public final final final Person copy(@NotNull String name, boolean boolean boolean drinking) { Intrinsics.checkNotNullParameter(name, "name"); return return return new new new Person(name, this this this.age, drinking); } @NotNull 30 semicolons included 30 semicolons included 30 semicolons included
- 52. data data data class class class Person(val val val name:String, val val val age:Int, val val val drinking:Boolean = true)
- 53. data data data class class class Person( val val val name:String, val val val age:Int, val val val drinking:Boolean = true )
- 54. data data data class class class Person( val val val names:List<String>, val val val lastName:String, val val val birthDate:LocalDate, val val val email:Email, val val val address:Address, val val val family:List<Person>, val val val drinking:Boolean = true )
- 55. In java there are In java there are In java there are records records records but unfortunately as but unfortunately as but unfortunately as for for for java 16 java 16 java 16 there is nothing like there is nothing like there is nothing like .copy(...) .copy(...) .copy(...) yet. yet. yet.
- 56. data class data class data class
- 57. data class data class data class Simple immutable record Simple immutable record Simple immutable record
- 58. PURE CODE RULES PURE CODE RULES PURE CODE RULES
- 59. The most important rule: The most important rule: The most important rule:
- 61. The most important rule: The most important rule: The most important rule:
- 62. Don't be like COVID-19 Don't be like COVID-19 Don't be like COVID-19
- 63. The most important rule: The most important rule: The most important rule:
- 64. Don't be like COVID-19 Don't be like COVID-19 Don't be like COVID-19
- 65. The most important rule: The most important rule: The most important rule:
- 66. Don't be like COVID-19 Don't be like COVID-19 Don't be like COVID-19 Do not mutate Do not mutate Do not mutate
- 69. IMMUTABILITY IMMUTABILITY IMMUTABILITY immutable records, objects immutable data structures
- 70. IMMUTABILITY IMMUTABILITY IMMUTABILITY immutable records, objects immutable data structures
- 71. vavr list vavr list vavr list val val val list1 = list(1, 2, 3) val val val list2 = list1.prepend(0) println(list1) println(list2) //List(1, 2, 3) //List(0, 1, 2, 3)
- 72. kotlin immutable (default list) kotlin immutable (default list) kotlin immutable (default list) val val val list1 = listOf(1, 2, 3) val val val list2 = listOf(0) + list1 // not efficient println(list1) println(list2) //[1, 2, 3] //[0, 1, 2, 3]
- 73. val val val list1 = listOf(1, 2, 3) val val val list2 = listOf(0) + list1 (list1 as as as MutableList)[1] = -1 println(list1) println(list2) //[1, -1, 3] //[0, 1, 2, 3]
- 74. java.util.ArrayList java.util.ArrayList java.util.ArrayList mutable by design mutable by design mutable by design val val val list1 = ArrayList(listOf(1,2,3)) for for for (el in in in list1 ) { list1.add(list1.size) } println(list1)
- 75. Not all Lists are created equal Not all Lists are created equal Not all Lists are created equal io.vavr.collection.List io.vavr.collection.List io.vavr.collection.List > > > kotlin.ImmutableList kotlin.ImmutableList kotlin.ImmutableList > > > java.util.List java.util.List java.util.List (for (for (for typical typical typical business business business code) code) code)
- 76. TYPE INFERENCE TYPE INFERENCE TYPE INFERENCE HAVING A TYPE BUT NOT TYPING THE TYPE
- 78. fun fun fun main() { val val val x = "Devoxx Poland" }
- 79. val variableName : OptionalType = ... val variableName : OptionalType = ... val variableName : OptionalType = ... class class class A(val val val fieldAndConstructorArf:B, onlyArg:String) { val val val fieldInitializedInClass = onlyArg+"_suffix" fun fun fun a(arg:Int):String {// :String not needed val val val variable = "$arg and $fieldInitializedInClass" val val val other:String = variable //:String not needed return return return other } }
- 80. val variableName : OptionalType = ... val variableName : OptionalType = ... val variableName : OptionalType = ... class class class A(val val val fieldAndConstructorArf:B, onlyArg:String) { val val val fieldInitializedInClass = onlyArg+"_suffix" fun fun fun a(arg:Int):String {// :String not needed val val val variable = "$arg and $fieldInitializedInClass" val val val other:String = variable //:String not needed return return return other } } one simple syntax rule - fits everywhere one simple syntax rule - fits everywhere one simple syntax rule - fits everywhere
- 81. Type inference means type safety Type inference means type safety Type inference means type safety
- 82. Type inference means type safety Type inference means type safety Type inference means type safety doubts? doubts? doubts?
- 83. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)?
- 84. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters
- 85. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character
- 86. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly
- 87. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly must be not like recent 20 passwords
- 88. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly must be not like recent 20 passwords or or or
- 89. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly must be not like recent 20 passwords or or or
- 90. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly must be not like recent 20 passwords or or or
- 91. Which password policy is better (safer)? Which password policy is better (safer)? Which password policy is better (safer)? at least 12 characters must include upper, lower case, digit and special character must be changed weekly must be not like recent 20 passwords or or or
- 93. typealias typealias typealias SecurityRegistry = HashMap<Security.Id,List<Either<Group,Us val val val x:SecurityRegistry = ...
- 94. NEXT STEP NEXT STEP NEXT STEP Expressions Expressions Expressions
- 96. ii i
- 97. Kill statements Kill statements Kill statements fun fun fun addWithStatements(a:Int, b:Int):Int { return return return a + b } fun fun fun addAsExpression(a:Int, b:Int) = a + b
- 98. Kill statements Kill statements Kill statements fun fun fun addWithStatements(a:Int, b:Int):Int { return return return a + b } fun fun fun addAsExpression(a:Int, b:Int) = a + b return return return is a younger brother of is a younger brother of is a younger brother of GOTO GOTO GOTO
- 99. Instructions are not funny Instructions are not funny Instructions are not funny
- 100. sealed sealed sealed class class class Order(val val val sum: Int) class class class Created(s: Int) : Order(s) class class class Paid(s: Int) : Order(s) class class class Delivered(s: Int) : Order(s)
- 101. sealed sealed sealed class class class Order(val val val sum: Int) class class class Created(s: Int) : Order(s) class class class Paid(s: Int) : Order(s) class class class Delivered(s: Int) : Order(s) val val val orders = list( Created(120), Paid(20), Delivered(30), Paid(40) )
- 102. sealed sealed sealed class class class Order(val val val sum: Int) class class class Created(s: Int) : Order(s) class class class Paid(s: Int) : Order(s) class class class Delivered(s: Int) : Order(s) val val val orders = list( Created(120), Paid(20), Delivered(30), Paid(40) ) fun fun fun impureSum(orders: Seq<Order>): Int { var var var sum = 0 for for for (order in in in orders) { when when when (order) { is is is Paid -> sum = sum + order.sum is is is Delivered -> sum = sum + order.sum } } return return return sum } fun fun fun main() { println(impureSum(orders)) //90 }
- 103. fun fun fun pureSum(orders: Seq<Order>): Int = orders.foldLeft(0, { accumulator, order -> when when when (order) { is is is Paid -> accumulator + order.sum is is is Delivered -> accumulator + order.sum is is is Created -> accumulator } }) fun fun fun main() = println(pureSum(orders)) //90
- 104. fun fun fun pureSum(orders: Seq<Order>): Int = orders.foldLeft(0) { accumulator, order -> when when when (order) { is is is Paid -> accumulator + order.sum is is is Delivered -> accumulator + order.sum is is is Created -> accumulator } } fun fun fun main() = println(pureSum(orders)) //90
- 105. fun fun fun pureSum(orders: Seq<Order>): Int = orders.foldLeft(0) { accumulator, order -> when when when (order) { is is is Paid -> accumulator + order.sum is is is Delivered -> accumulator + order.sum is is is Created -> accumulator } } fun fun fun main() = println(pureSum(orders)) //90 fold - don't loop fold - don't loop fold - don't loop
- 106. One day ... One day ... One day ...
- 108. One day ... One day ... One day ...
- 109. Business: We have to add new types of orders Business: We have to add new types of orders Business: We have to add new types of orders
- 110. sealed sealed sealed class class class Order(val val val sum: Int) class class class Created(s: Int) : Order(s) class class class Paid(s: Int) : Order(s) class class class Delivered(s: Int) : Order(s) //new guy class class class Cancelled(s:Int) : Order(s) //new guy class class class Archived(s:Int) :Order(s) val val val orders = list( Created(120), Paid(20), Delivered(30), Paid(40), Cancelled(20), Archived(10) )
- 111. fun fun fun impureSum(orders: Seq<Order>): Int { var var var sum = 0 for for for (order in in in orders) { when when when (order) { is is is Paid -> sum = sum + order.sum is is is Delivered -> sum = sum + order.sum } } return return return sum //90 - wrong }
- 112. fun fun fun impureSum(orders: Seq<Order>): Int = orders.foldLeft(0) { accumulator, order -> when when when (order) { // Error: 'when' expression must be exhaustive, // add necessary 'is Cancelled', 'is Archived' branches // or 'else' branch instead is is is Paid -> accumulator + order.sum is is is Delivered -> accumulator + order.sum is is is Created -> accumulator } } //wont compile
- 113. Compiler is like your BEST friend. Compiler is like your BEST friend. Compiler is like your BEST friend. Best friend: Best friend: Best friend: Will tell you the truth even if You do not want to hear Will tell you the truth even if You do not want to hear Will tell you the truth even if You do not want to hear it it it Compiler will Compiler will Compiler will tell you that your code will eventually crash on tell you that your code will eventually crash on tell you that your code will eventually crash on production. production. production.
- 114. if if if ,, , when when when,, , try try try etc. are expressions in Kotlin etc. are expressions in Kotlin etc. are expressions in Kotlin use them use them use them fun (a:Int,b:Int) = a + if if if (b<5) a else else else -a
- 115. Even More safety Even More safety Even More safety
- 116. sealed sealed sealed class class class Order(internal internal internal val val val sum: Int) { open open open fun fun fun income(): Int = sum fun fun fun cancelled() = Cancelled(this this this) } class class class Created(s: Int) : Order(s) { override override override fun fun fun income(): Int = 0 fun fun fun pay() = Paid(this this this) } // cannot create Paid without seeing first ordser in Created state class class class Paid internal internal internal constructor constructor constructor(order: Created) : Order(order.sum) { fun fun fun deliver() = Delivered(this this this) } [...] val val val orders = list( Created(120), Created(20).pay(), Created(30).pay().deliver(), Created(40).pay(), Created(20).pay().cancelled(), Created(30).pay().deliver().archive() ) fun fun fun pureSum(orders: Seq<Order>): Int = orders.foldLeft(0) { accumulator, order -> accumulator + order.income() } fun fun fun main() {
- 117. fun fun fun perfectDelivery() = run { val val val created = Created(25) val val val paid = created.pay() paid.deliver() }
- 118. SIDE EFFECTS SIDE EFFECTS SIDE EFFECTS
- 119. SIDE EFFECTS SIDE EFFECTS SIDE EFFECTS Functional programming is all about side Functional programming is all about side Functional programming is all about side effects effects effects
- 120. class class class Paid internal internal internal constructor constructor constructor(order: Created) : Order(order.sum) { fun fun fun deliver() = Delivered(this this this).also { println("delivered") } fun fun fun deliverFast() = Delivered(this this this).also { println("delivered fast") } }
- 121. fun fun fun perfectDelivery() = run { val val val created = Created(25) val val val paid = created.pay() paid.deliver() }
- 122. Surprise Surprise Surprise fun fun fun doubleDelivery() = run { val val val created = Created(25) val val val paid = created.pay() paid.deliver() if if if (paid.income() > 20) { paid.deliverFast() } } fun fun fun main() = doubleDelivery() //delivered //delivered fast
- 123. SIDE EFFECTS DONE PURELY SIDE EFFECTS DONE PURELY SIDE EFFECTS DONE PURELY How to not have surprises (that often) How to not have surprises (that often) How to not have surprises (that often)
- 124. a fail a fail a fail fun fun fun sayIt() = println("I am just dirty side effect")
- 125. fun fun fun sayItLater() = { println("No side effects")}
- 126. fun fun fun sayItLater() = { println("No side effects")} fun fun fun main() = run { sayItLater() //nothing val val val x = sayItLater() // nothing x() //"No side effects" (there it happens) }
- 127. Back to the problem: Back to the problem: Back to the problem: fun fun fun crashDelivery() = run { val val val created = Created(25) val val val paid = created.pay() paid.deliver() if if if (paid.income() > 20) { paid.deliverFast() } }
- 128. Naleśnik == PanCake Naleśnik == PanCake Naleśnik == PanCake
- 130. class class class Naleśnik<out A>(private private private val val val inside: () -> A) { fun fun fun <B> map(f: (A) -> B) = Naleśnik { f(this this this.inside()) } fun fun fun <B> flatMap(f: (A) -> Naleśnik<B>): Naleśnik<B> = Naleśnik { f(this this this.inside()).inside() } fun fun fun unsafeRun(): A = inside() //use with caution }
- 131. sealed sealed sealed class class class Order(internal internal internal val val val sum: Int) { open open open fun fun fun income(): Int = sum fun fun fun cancelled() = Naleśnik { Cancelled(this this this) } } class class class Created(s: Int) : Order(s) { override override override fun fun fun income(): Int = 0 fun fun fun pay() = Naleśnik { Paid(this this this) } } class class class Paid internal internal internal constructor constructor constructor(order: Created) : Order(order.sum) { fun fun fun deliver(): Naleśnik<Delivered> = Naleśnik { Delivered(this this this).also { println("delivered") } } fun fun fun deliverFast(): Naleśnik<Delivered> = Naleśnik { Delivered(this this this).also { println("delivered fast") } } }
- 132. fun fun fun crashDelivery():Naleśnik<Delivered> = run { val val val created = Created(25) val val val paid = created.pay() val val val delivered = paid.flatMap { it.deliver() } paid.flatMap { if if if (it.income()> 20) it.deliverFast() else else else it.de } fun fun fun main() { crashDelivery().unsafeRun() //delivered fast }
- 133. Naleśnik / pancake - harder to mess side Naleśnik / pancake - harder to mess side Naleśnik / pancake - harder to mess side effects effects effects
- 134. Naleśnik > Burrito Naleśnik > Burrito Naleśnik > Burrito
- 135. Naleśnik Naleśnik Naleśnik == IO (Monad) == IO (Monad) == IO (Monad)
- 136. IO <A> IO <A> IO <A> ~= ~= ~= Mono<A> Mono<A> Mono<A>
- 137. in in in arrow-fx arrow-fx arrow-fx IO<A> IO<A> IO<A> == == == suspend () -> A suspend () -> A suspend () -> A
- 139. Transaction is a Monad Transaction is a Monad Transaction is a Monad class class class Transaction<A>(private private private val val val action: (Connection) -> A) { fun fun fun <B> map ( f: (A)->B) = Transaction { conn -> f(action(conn))} fun fun fun <B> flatMap( f: (A)->Transaction<B>) = Transaction { conn -> f(action(conn)).action(conn) } fun fun fun runTransaction(conn:Connection): Either<Exception, A> = run { val val val initialAC = conn.autoCommit conn.autoCommit = false try try try { val val val res = action(conn) conn.commit() Either.right(res) } catch catch catch (e: Exception) { conn.rollback() Either.left(e) } finally finally finally { conn.autoCommit = initialAC } } }
- 140. GENERIC SIDE EFFECTS IO<R,E,A> IO<R,E,A> IO<R,E,A> R - environment (dependencies) E - error (not only exception) A - result (business)
- 141. Scala ZIO Scala ZIO Scala ZIO
- 142. NEE mutilated mutilated mutilated ZIO <R,E,A> ZIO <R,E,A> ZIO <R,E,A> + spring like aspects + spring like aspects + spring like aspects description description description
- 143. Do not write: Do not write: Do not write: class class class Hasiok { @Resource val val val jdbcConnection: Connection @Transactional @Secure @Cacheable @Retryable fun fun fun f(p:P) { //code } }
- 144. Write like: Write like: Write like: class class class Hasiok { fun fun fun enterprisyFunction(x:Int) = Nee.pure( secure + retryable + cache.of(x) + tx ) {jdbcConnection:Connection -> //code using jdbcConnection } //declaration above means security is checked before retrial //and retrial is made before cache which happens before transacti }
- 145. FRAMEWORKS FRAMEWORKS FRAMEWORKS Kotlin ktor (web) arrow-kt, arrow-fx (effects) Nee (experiemental) https://github.com/colomboe/KIO
- 146. HOW TO PROTECT PURITY HOW TO PROTECT PURITY HOW TO PROTECT PURITY
- 147. HOW TO PROTECT PURITY HOW TO PROTECT PURITY HOW TO PROTECT PURITY
- 148. What about discipline What about discipline What about discipline
- 150. TOOLS TOOLS TOOLS
- 152. Plugin for Plugin for Plugin for detekt detekt detekt
- 153. Plugin for Plugin for Plugin for detekt detekt detekt Rule Detects Properties with defaults Requires i LoopUsage use of for, while active: true ReturnStatement use of return statement active: true VariableUsage use of var active: true ReturnUnit use of function returning Unit, Nothing, Void active: true checkFunctionType: true :ballot_box_with_check: ClassDefinition use of object-oriented class active: false AbstractClassDefinition use of object-oriented abstract class active: false ThrowExpression use of throw active: true MutableCollections use of mutable collections active: true :ballot_box_with_check: BranchStatement use of if or when as statement :white_check_mark: MissingElse use of if statement without else type resolution
- 154. PURE CODE NOS PURE CODE NOS PURE CODE NOS
- 155. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var)
- 156. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops
- 157. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions
- 158. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions no void (Unit)
- 159. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions no void (Unit) no return
- 160. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions no void (Unit) no return no throw
- 161. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions no void (Unit) no return no throw no mercy
- 162. PURE CODE NOS PURE CODE NOS PURE CODE NOS no variables (var) no loops no instructions no void (Unit) no return no throw no mercy with the exception of main
- 163. DO YOU NEED FP? DO YOU NEED FP? DO YOU NEED FP?
- 166. Who needs calculator if all we do is adding Who needs calculator if all we do is adding Who needs calculator if all we do is adding things like things like things like 123 + 352 123 + 352 123 + 352
- 168. Who needs electronic calc if all we do is Who needs electronic calc if all we do is Who needs electronic calc if all we do is multiplying things like multiplying things like multiplying things like 323 *3 323 *3 323 *3
- 170. Who needs computer calc if divide and multiply Who needs computer calc if divide and multiply Who needs computer calc if divide and multiply few numbers few numbers few numbers
- 171. For someone having experience with abacus For someone having experience with abacus For someone having experience with abacus only - this machine is useless only - this machine is useless only - this machine is useless
- 172. FP ROAD FP ROAD FP ROAD Immutability Expressions Type safety Monads
- 173. PROJECT LINKS PROJECT LINKS PROJECT LINKS example of pure todo list with arrow-fx and example of pure todo list with arrow-fx and example of pure todo list with arrow-fx and ktor ktor ktor springy effects for kotlin springy effects for kotlin springy effects for kotlin example ktor project with Nee ("todo list like") example ktor project with Nee ("todo list like") example ktor project with Nee ("todo list like") https://github.com/neeffect/kure-potlin https://github.com/neeffect/kure-potlin https://github.com/neeffect/kure-potlin https://github.com/jarekratajski/just_another_to https://github.com/jarekratajski/just_another_to https://github.com/jarekratajski/just_another_to https://github.com/neeffect/nee https://github.com/neeffect/nee https://github.com/neeffect/nee https://github.com/neeffect/kotlin-stones https://github.com/neeffect/kotlin-stones https://github.com/neeffect/kotlin-stones
- 177. SUMMARY SUMMARY SUMMARY FP FP FP The more complex program we write the more The more complex program we write the more The more complex program we write the more it helps it helps it helps
- 179. SUMMARY SUMMARY SUMMARY FP FP FP The more complex program we write the more The more complex program we write the more The more complex program we write the more it helps it helps it helps It is not a sliver bullet It is not a sliver bullet It is not a sliver bullet
- 181. SUMMARY SUMMARY SUMMARY FP FP FP The more complex program we write the more The more complex program we write the more The more complex program we write the more it helps it helps it helps It is not a sliver bullet It is not a sliver bullet It is not a sliver bullet It's a long way. But there are many convenient It's a long way. But there are many convenient It's a long way. But there are many convenient steps steps steps
- 183. SUMMARY SUMMARY SUMMARY FP FP FP The more complex program we write the more The more complex program we write the more The more complex program we write the more it helps it helps it helps It is not a sliver bullet It is not a sliver bullet It is not a sliver bullet It's a long way. But there are many convenient It's a long way. But there are many convenient It's a long way. But there are many convenient steps steps steps Each step is a potential Each step is a potential Each step is a potential profit profit profit
- 185. SUMMARY SUMMARY SUMMARY FP FP FP The more complex program we write the more The more complex program we write the more The more complex program we write the more it helps it helps it helps It is not a sliver bullet It is not a sliver bullet It is not a sliver bullet It's a long way. But there are many convenient It's a long way. But there are many convenient It's a long way. But there are many convenient steps steps steps Each step is a potential Each step is a potential Each step is a potential profit profit profit
- 186. Kotlin is not Scala - but with some Kotlin is not Scala - but with some Kotlin is not Scala - but with some tools/constraints it can be quite pure tools/constraints it can be quite pure tools/constraints it can be quite pure