Groovy for Domain-specific Languages - Second Edition

Closure return values

Closure declarations syntax provides no means of defining a return value. Every closure does, however, return a value with each invocation. A closure can have explicit return statements. If a return statement is encountered, then the value defined in the return statement is returned; otherwise, execution continues until the last statement in the closure block:

given: "a closure that returns values"
def closure = { param ->
    if (param == 1)
        return 1
    2
}
expect:
closure(1) == 1  // return statement reached
closure(-1) == 2 // ending statement evaluates to 2

If no return statement is encountered, then the value returned by the closure is the result of evaluating the last statement encountered in the closure block. If the last statement ...