groovy.lang.MissingPropertyException：无此类属性：类的所有者：母亲

Question

I'm working on the following code:

caught exception at 'this.owner' which in the Closure of birth method.

class Mother {
            int field = 1
            int foo(){
                return 2
            }
            Closure birth(param){
                def local = 3
                def closure = {caller -> [this,field,foo(),local,param,caller,this.owner]} 
                return closure
            }
        }

        Mother m = new Mother();
        closure = m.birth(4);

        context = closure.call(this);
        println context[0].class.name

        assert context[1..4] == [1,2,3,4]
        assert context[5] instanceof Script
        assert context[6] instanceof Mother

        fClosure = m.birth(4);
        sClosure = m.birth(4);
        assert false == fClosure.is(sClosure)

Which, when run finishes with:

'this.owner' caught groovy.lang.MissingPropertyException: No such property: owner for class: Mother

Why is that?

Answer 1

It all works well, please have a look here , especially:

this corresponds to the enclosing class where the closure is defined

Since corresponding class is Mother and it has no owner field nor property defined it fails with MPE. If you define owner on Mother class it will run (and possibly fail with another exception).