is it possible to break out of closure in groovy

Question

is there a way to 'break' out of a groovy closure.

maybe something like this:

[1, 2, 3].each { 
  println(it)
  if (it == 2)
    break 
}

Answer 1

You can throw an exception:

try {
    [1, 2, 3].each { 
        println(it)
        if (it == 2)
            throw new Exception("return from closure") 
    }
} catch (Exception e) { }

Use could also use "findAll" or "grep" to filter out your list and then use "each".

[1, 2, 3].findAll{ it < 3 }.each{ println it }

Answer 2

Take a look at Best pattern for simulating continue in groovy closure for an extensive discussion.

Answer 3

Edited.

[1, 2, 3].each { 
  if (it == 2) return
  println(it)
}

Think of the closure like a little method. How would you break out of a method? You return. Return will break out of the closure.

You cannot break out of the iteration just as you couldn't break out of the following code.

doThings([0,1,3])

void doThings(List things) {
    for (i in things) {
        printIt(i)
    }
}

void printIt(Object it) {
    if(it == 2) break // This is not possible beacuse you arn't inside a loop
    println it
}

This almost exactly what Groovy is doing when you call the each METHOD and pass it a closure.

Something you might want to consider for your particular case: the find or findAll methods.

[1,2,3].findAll { it < 2 }.each { println it }

I hope this helps you understand what is going on.

Answer 4

I often forget that Groovy implements an "any" method.

[1, 2, 3].any {
println it
return (it == 2) }​