setTimeout for a function of a private object

Question

I'm trying to set timeout to a function of an object, which is a private function of another object. Actually the structure is something like this:

function MainObject() {
    var id;
    ...
    var InnerObject = function() {
        this.getSomething = function() { ... }
    }

    this.testFunc = function() {
        id = setTimeout(InnerObject.getSomething(), 1000);
    }
}

...and it won't work as it says 'undefined' when trying to set timeout, and I can't execute this function directly as it's a private function. What am I doing wrong? Tried to find something particular but didn't success. I see the error might be somewhere in scope problems, but still don't get it

Answer 1

Since you've given us little to go on for why you've chosen a complicated approach, I will simplify things into something that will work.

function MainObject() {
    var id;
    ...
    function getSomething() {
        // code here
    }

    this.testFunc = function() {
        id = setTimeout(getSomething, 1000);
    }
}

Things wrong with your approach:

1. InnerObject looks a constructor function, but you never actually call it.
2. Because InnerObject is a constructor function, there is no InnerObject.getSomething property. If you did var obj = new InnerObject(), then there would be an obj.getSomething property you could call.
3. You pass a function reference to setTimeout(). Unless getSomething() returns a function, you don't want to call it, you would want to pass just the function reference without the parens.

---

If you really wanted to keep the InnerObject, then you'd have to actually instantiate an object with that constructor like this:

function MainObject() {
    var id;
    ...
    var InnerObject = function() {
        this.getSomething = function() { ... }
    }
    // call your constructor and create an object
    var obj = new InnerObject();

    this.testFunc = function() {
        id = setTimeout(obj.getSomething.bind(obj), 1000);
    }
}

Note: the .bind(obj) is used so that the this pointer is set correctly when getSomething() is called by the timer code.