Scala: How to “store” a function in a var

anonymous-functionscala

I'm learning Scala and I'm trying to store a function in a var to evaluate it later:

var action:() => Any = () => {}
def setAction(act: => Any) {
    action = act 
}

but that doesn't compile:

error: type mismatch;
found: Any
required: () => Any
action = act

So it seems to me that in action = act instead of assigning the function it's evaluating it and assigning the result.
I canĀ“t find out how to assign the function without evaluating it.

Thanks!

Best Solution

Note type "() => Any" is not the same as by-name parameter "=> Any". Type "() => Any" is a function that takes no parameter and returns Any, whereas by-name parameter "=> Any" delays execution of the parameter until it's used and returns Any.

So what you need to do here is the following:

var action: () => Any = null

def setAction(act: => Any) = action = () => act

setAction(println("hello")) // does not print anything

action() // prints "hello"

setAction(123)

action() // returns 123
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