Question

I have defined two classes in javascript as follows.

function ParentClass(){
    this.one = function(){
      alert('inside one of parent');
    };

    this.two = function(){
       alert('inside two of parent');
       //this is just a skeleton of the actual FB.api implementation in my code
       FB.api('/me', 'post', function(response){
        this.one();
      });

    };

}

function ChildClass(){
    ParentClass.call(this);

    //overriding the one() in ParentClass
    this.one = function(){
      alert('inside one of child');
    };
}


ChildClass.prototype = new ParentClass();
ChildClass.prototype.constructor = ChildClass;
var c = new ChildClass();
c.two(); 

the last line calls the ParentClass's two() method which then calls the one() method overriden by the ChildCLass.

I get an error saying “this.one() is not defined”. But when I put the this.one() method outside the FB.api response block the function gets called perfectly. I think the problem might be that the ‘this’ in this.one() is referring to the FB.api callback function instead of the ChildClass. How do I solve this?

Answer 1

Just stash a copy of this in another variable outside the FB call.

this.two = function(){
   alert('inside two of parent');
   //this is just a skeleton of the actual FB.api implementation in my code
   var self = this;
   FB.api('/me', 'post', function(response){
    self.one();
  });

};