Question

Possible Duplicate:
Crockford’s Prototypal inheritance – Issues with nested objects

I’m having a problem getting the following code to execute a function in prototype B from prototype A, and was wondering if there was any easy solution:

var Ob = function () {
  test = 'hi';
}

Ob.prototype.A = {
  that : this,
  root : this,
  goB : function () {
    var that = this;

    console.log('hello');
    that.B.wtf();
  }
}

Ob.prototype.B = {
  that : this,
  root : this,
  wtf : function () {
    var that = this;

    console.log(that);
  }
}

test = new Ob;
test.A.goB();

Answer 1

You need to wire up your properties after the object has been created:

var Ob = function () {
    var that = this;

    // set the current root to this instance and return the object
    this.getA = function() {
        that.A.currentRoot = that;
        return that.A;
    };

    this.getB = function() {
        that.B.currentRoot = that;
        return that.B;
    };
};

Ob.prototype.A = {
    goB : function () {
        var that = this.currentRoot;

        console.log('hello');
        that.getB().wtf();
    }
};

Ob.prototype.B = {
    wtf : function () {
        var that = this.currentRoot;

        console.log(that, this);
    }
};


test = new Ob;
test.getA().goB();

A rather dirty hack is to use a privileged method in the parent object to augment the child object and return it so you have access to the parent object via a property. The dirty part is that if you cache the object the property is not guaranteed to have the correct value. So this is more or less a way to do it although you really shouldn’t do it this way.