Scala is a general-purpose programming language that is object-oriented, functional, and type-safe. It runs on the Java Virtual Machine and Common Language Runtime. Scala combines object-oriented and functional programming in a statically typed programming language. It is designed to express common programming patterns in a concise, elegant, and type-safe way.

14. Scala
the smarter cousin
David Rosell

15. Scala
the smarter cousin

16. Scala
the smarter cousin
Object Oriented
Functional

17. Scala
the smarter cousin
general-purpose, type-safe
Object Oriented
Functional

18. Scala
the smarter cousin
general-purpose, type-safe
Object Oriented
Functional
runs on JVM (and CLR)

20. OOP
as it should be done
Collections
Scala are
library oriented
Duck typing
Equals DSL’s
n!
= 1*2*3*...*n

21. Closures

23. scala> var more = 1
more: Int = 1
scala> val addMore = (x: Int) => x + more
addMore: (Int) => Int = <function>

24. scala> var more = 1
more: Int = 1
scala> val addMore = (x: Int) => x + more
addMore: (Int) => Int = <function>
scala> addMore(1)
res1: Int = 2
scala> more = 10
more: Int = 10
scala> addMore(1)
res3: Int = 11

26. Using
resources

27. def writeSomething(file: File): Unit = {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}

28. def writeSomething(file: File): Unit = {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}

29. def writeSomething(file: File): Unit = {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}
object WriteToFileSpecs extends Specification {
...
}

30. def writeSomething(file: File): Unit = {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}
“calling writeSomething must write to file” in {
val file = new File(“test.txt”)
try {
writeSomething(file)
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1)
} finally {
file.delete
}
}

31. def writeSomething(file: File) {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}
“calling writeSomething must write to file” in {
val file = new File(“test.txt”)
try {
writeSomething(file)
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1)
} finally {
file.delete
}
}

32. writer.println(“Hello Kitty”)
writer.println(new Date)
“calling writeSomething must write to file” in {
val file = new File(“test.txt”)
try {
writeSomething(file)
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) ??? how to test a ‘now’-date
} finally {
file.delete
}
}

33. def writeSomething(file: File) {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}

34. def writeSomething(file: File) {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
writer.println(new Date)
} finally {
writer.close
}
}

35. writer.println(“Hello Kitty”)
writer.println(new Date)
def writeSomething(file: File) {
val writer = new PrintWriter(file)
try {
} finally {
writer.close
}
}

36. Background
val list = List(“Pelle”, “Stina”)
for (name <- list) {
println(name)
}

37. Background
val list = List(“Pelle”, “Stina”)
list.foreach( aFunc(...) )

38. Background
val list = List(“Pelle”, “Stina”)
list.foreach( aFunc(...) )
def aFunc(s: String): Unit = {
println(s)
}

39. Background
def aFunc(s: String): Unit = {
println(s)
}
val list = List(“Pelle”, “Stina”)
list.foreach( (s: String): Unit => { println(s) } )

40. Background
def aFunc(s: String): Unit = {
println(s)
}
val list = List(“Pelle”, “Stina”)
list.foreach( (s: String) => { println(s) } )

41. Background
def aFunc(s: String): Unit = {
println(s)
}
val list = List(“Pelle”, “Stina”)
list.foreach( s => println(s) )

42. Background
def aFunc(s: String): Unit = {
println(s)
}
val list = List(“Pelle”, “Stina”)
list.foreach( _ => println(_) )

43. Background
def aFunc(s: String): Unit = {
println(s)
}
val list = List(“Pelle”, “Stina”)
list.foreach( println(_) )

44. Background
val list = List(“Pelle”, “Stina”)
list.foreach( println _ )

45. Background
val list = List(“Pelle”, “Stina”)
list.foreach( println _ )
for (name <- list) {
println(name)
}

46. def writeTo(file: File) {
val writer = new PrintWriter(file)
try {
writer.println(“Hello Kitty”)
...
writer.println(new Date)
} finally {
writer.close
}
}

47. writer.println(“Hello Kitty”)
writer.println(new Date)
def writeTo(file: File) {
val writer = new PrintWriter(file)
try {
...
} finally {
writer.close
}
}

48. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
def writeTo(file: File) {
val writer = new PrintWriter(file)
try {
...
} finally {
writer.close
}
}

49. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
def writeTo(file: File) {
val writer = new PrintWriter(file)
try {
...
} finally {
writer.close
}
}

50. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
def writeTo(file: File) {
val writer = new PrintWriter(file)
try {
...
} finally {
writer.close
}
}

51. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}

52. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
...
} finally {
writer.close
}
}

53. def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}

54. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
def op(writer: PrintWriter) {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
val file = new File(“test.txt”)
val op = (writer: PrintWriter) => {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
writeTo(file, op)

55. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
val op = (writer: PrintWriter) => {
writer.println(“Hello Kitty”)
writer.println(new Date)
}
writeTo(file, op)

56. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writeTo(file, (writer: PrintWriter) => {
op)
writer.println(“Hello Kitty”)
writer.println(new Date)
}

57. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writeTo(file, (writer: PrintWriter) => {
writer.println(“Hello Kitty”)
writer.println(new Date)
})

58. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writer => {
writer.println(“Hello Kitty”)
writer.println(new Date)
}

59. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writeTo(file, writer => {
writer.println(“Hello Kitty”)
writer.println(new Date)
})

60. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}

61. )(
def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}

62. Currying
)(
def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}

63. )(
def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writeTo(file)(writer =>
writer.println(“Hello Kitty”)
writer.println(new Date))

64. def writeTo(file: File)(op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
val file = new File(“test.txt”)
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(new Date)
}

65. “calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
writeTo(file)
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) ??? how to test a ‘now’-date
} finally {
file.delete
}
}

66. writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(new Date)
}
“calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
writeTo(file)
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) ??? how to test a ‘now’-date
} finally {
file.delete
}
}

67. “calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(new Date)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) ??? how to test a ‘now’-date
} finally {
file.delete
}
}

68. “calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(new Date)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) ??? how to test a ‘now’-date
} finally {
file.delete
}
}

69. “calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
} finally {
file.delete
}
}

70. def writeTo(file: File, op: PrintWriter => Unit) {
val writer = new PrintWriter(file)
try {
op(writer)
} finally {
writer.close
}
}
“calling writeTo must write to file” in {
val file = new File(“test.txt”)
try {
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
} finally {
file.delete
}
}

71. “calling writeSomething must write to file” in {
val file = new File(“test.txt”)
try {
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
} finally {
file.delete
}
}

72. “calling writeSomething must write to file” in {
withFile { file =>
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
}
}
def withFile(op: File => Unit) {
val file = new File(“test.txt”)
try {
op(file)
} finally {
file.delete
}
}

73. “calling writeSomething must write to file” in {
withFile { file =>
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
}
}

74. “calling writeSomething must write to file” in {
withFile { file =>
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
val cont = Source.fromFile(file).getLines.toList
validate(file) { cont =>
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
}
}

75. “calling writeSomething must write to file” in {
withFile { file =>
val now = new Date
writeTo(file) { writer =>
writer.println(“Hello Kitty”)
writer.println(now)
}
validate(file) { cont =>
cont(0) must be equalTo “Hello Kitty”
cont(1) must be equalTo now.toString
}
}
}
def validate(file: File)(op: List[String] => Unit) {
val cont = Source.fromFile(file).getLines.toList
op(cont)
}

76. def withFile(op: File => Unit) {
val file = new File(“test.txt”)
try {
op(file)
} finally {
file.delete
}
}
def validate(file: File)(op: List[String] => Unit) {
val cont = Source.fromFile(file).getLines.toList
op(cont)
}

77. def withFile(op: File => Unit) {
val file = new File(“test.txt”)
try {
op(file)
} finally {
file.delete
}
}
def validate(file: File)(op: List[String] => Unit) {
val cont = Source.fromFile(file).getLines.toList
op(cont)
}

78. object WriteToFileSpecs extends Specification with TestFileHelper {
...
}
trait TestFileHelper {
def withFile(op: File => Unit) {
val file = new File(“test.txt”)
try {
op(file)
} finally {
file.delete
}
}
def validate(file: File)(op: List[String] => Unit) {
val cont = Source.fromFile(file).getLines.toList
op(cont)
}
}

83. JVM Community
Language

84. JVM Community

85. Scala gives
• More concise - type inference
• More expressive - operator notation
• OOP for real
• Slick functional collection api
• Full access to Java

87. 1’st edition free
http://www.artima.com/
pins1ed/

88. David Rosell

89. David Rosell
BlogSpot: http://drsimplestuff.blogspot.com
GitHub: https://github.com/daros
E-mail: david.rosell@redpill-linpro.com