Assignments

Assignment in Scala follows more or less the same rules as Java and other related rules. There are some differences.

Increment operators do not work (i++). As I understand it the rational is that it is too specific an idiom. There is not an easy way to generalize it. Instead you must use i += 1.

Assignments do not return a value. For example you cannot do val i = j = 2 or while( (i = read(buffer)) > 0 ){...}.

One feature that is fairly unique in Scala is the ability to expand a case-class or other class that has an associated extractor. For details look at the previous topic Assignment and Parameter Objects.

Examples:

1. scala> val i,j=2
2. i: Int = 2
3. j: Int = 2
5. scala> val (i,j) = (1,2)
6. i: Int = 1
7. j: Int = 2
9. scala> val (i,j,k) = (1,"two",3.0)
10. i: Int = 1
11. j: java.lang.String = two
12. k: Double = 3.0
14. scala> case class Data( name:String, age:Int, weight:Float)
15. defined class Data
17. scala> val Data(name, age, weight) = Data("Jesse", 133, 100f)
18. name: String = Jesse
19. age: Int = 133
20. weight: Float = 100.0
22. scala> val value = 1
23. value: Int = 1
25. scala> i += 1
26. :10: error: reassignment to val
27.        i += 1
28.          ^
30. scala> var variable = 1
31. variable: Int = 1
33. scala> variable += 1
35. scala> println(variable)
36. 2