Incrementing and getting value

Question

Simple scala question. Consider the below.

scala> var mycounter: Int = 0;
mycounter: Int = 0

scala> mycounter += 1

scala> mycounter
res1: Int = 1
         


        

Answer 1

Using '+=' return Unit, so you should do:

{ mycounter += 1; mycounter }

You can too do the trick using a closure (as function parameters are val):

scala> var x = 1
x: Int = 1

scala> def f(y: Int) = { x += y; x}
f: (y: Int)Int

scala> f(1)
res5: Int = 2

scala> f(5)
res6: Int = 7

scala> x
res7: Int = 7

BTW, you might consider using an immutable value instead, and embrace this programming style, then all your statements will return something ;)

Answer 2

Assignment is an expression that is evaluated to Unit. Reasoning behind it can be found here: What is the motivation for Scala assignment evaluating to Unit rather than the value assigned?

In Scala this is usually not a problem because there probably is a different construct for the problem you are solving.

I don't know your exact use case, but if you want to use the incrementation it might be in the following form:

(1 to 10).foreach { i => 
  // do something with i
}

Answer 3

Sometimes I do this:

val nextId = { var i = 0; () => { i += 1; i} }
println(nextId())                               //> 1
println(nextId())                               //> 2

Might not work for you if you need sometime to access the value without incrementing.