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Features of Kotlin I find exciting

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This short talk covers a few awesome things in Kotlin which make the language a lot more enjoyable.

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Features of Kotlin I find exciting

  1. 1. July 2018 Robert MacLean @rmaclean
  2. 2. 3 Robert MacLean @rmaclean SADEV.co.za
  3. 3. 4 Basic Pascal Delphi PHP Perl C# JavaScript TypeScript Java Kotlin
  4. 4. C# 5 Kotlin var name = ""; ... if (name != null) { } var member = existing ?? new Person(); var name = "" name = null // NOPE! var name : String? = "" var member = existing ?: Person()
  5. 5. C# 6 Kotlin var person = new Person(); ... if (person?.name != null) { } var person? = Person() ... if (person?.name != null) { } var s : String? = null println(s.length) // won’t compile println(s?.length) // null println(s!!.length) // NPE
  6. 6. JavaScript 7 Kotlin let numbers = [1, 5, 6, 7, 8]; let evens = numbers .filter(num => num % 2 === 0); val numbers = listOf(1, 5, 6, 7, 8) var evens = numbers .filter({ num -> num % 2 == 0 }) evens = numbers.filter({ it % 2 == 0 })
  7. 7. Java 8 Kotlin foo.is(bar) public void should_have_visible_logout() { } foo.`is`(bar) fun `should have visible logout`() { }
  8. 8. C# 9 Kotlin throw new Exception(); // compiler will tell you this won’t execute void start() { while (true) { ... } } start(); // compiler totally happy fun start():Nothing { while (true) { ... } } start() // compiler will tell you this won’t execute onwards!
  9. 9. Java 10 Kotlin public class Person { private String name; private int age = 0; public Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; if (name != null ? !name.equals(person.name) : person.name != null) return false; if (age != 0 ? age != person.age : person.age != 0) return false; } @Override public int hashCode() {
  10. 10. public class Person { private String name; private int age = 0; public Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; if (name != null ? !name.equals(person.name) : person.name != null) return false; if (age != 0 ? age != person.age : person.age != 0) return false; } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; result = 31 * result + age; return result; } @Override public String toString() { return "Person{" + "name='" + name + ''' + ", age='" + age + ''' + '}'; } }
  11. 11. C# 12 Kotlin class Person { public int Age {get; set;} public string Name {get; set;} public Person(int Age, string Name){ this.Age = Age; this.Name = Name; } }
  12. 12. Java 13 Kotlin public class Person { private String name; private int age = 0; public Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; if (name != null ? !name.equals(person.name) : person.name != null) return false; if (age != 0 ? age != person.age : person.age != 0) return false; } @Override public int hashCode() { data class User(val name: String, val age: Int)
  13. 13. 14 Kotlin 101 29 August CodeBridge in Newlands http://bit.ly/kotlin101
  14. 14. 15 ExpertDrinks 2 August http://bit.ly/expertdrinks
  15. 15. Robert MacLean Twitter @rmaclean Web sadev.co.za 16

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