Groovy delegates working as intended?

问题

I have a short snippet where I try to delegate the variable resolution to the delegate. However the delegates value isnt used, instead the owners value is used. Is this intentional or is this a bug?

class Person {
    int age
}

def age = -5
def closure = { -> age }
closure.delegate = new Person(age: 99)
closure.resolveStrategy == Closure.DELEGATE_ONLY

assert closure.call() == 99

Above code fails, with the closure returning -5.

回答1:

Your code returns -5 because the variable age is defined withing the lexical scope of the closure, meaning that the closure can use the value of the variable age.

You have to explicitly tell the closure to use the age property of the delegate:

def closure = { -> delegate.age }

Try the following code:

class Person {
    int age
}  
def age = -5 
def closure = { -> delegate.age * age } 
closure.delegate = new Person(age: 99)
closure.resolveStrategy == Closure.DELEGATE_ONLY 
assert closure.call() == 99*-5

来源：https://stackoverflow.com/questions/32368483/groovy-delegates-working-as-intended