OOP, the new operator & object literal notation - multiple child objects of a parent

[iporter]

I wonder if anyone can clear up an OOP issue for me, specifically, how to have multiple child objects of a parent object. Consider the code below:

var parentObj={
childCount: 0,
childObj: {
id:false,
init: function() {
alert(this.id);
parentObj.childCount++;
this.id = parentObj.childCount;
alert("Child " + this.id + " Created");
}
}
}

Calling 'parentObj.childObj.init();', the first alert produces 'undefined' and the second 'Child 1 Created'. A second call to 'parentObj.childObj.init();' produces the '1' from above instead of the 'undefined' I'm expecting - I realise this is because I'm working with the same object.

However, calling 'var firstChild = parentObj.childObj.init(); var secondChild = parentObj.childObj.init()' produces the same result (as does 'var firstChild = parentObj.childObj; firstChild.init().

I've also tried the 'new' operator. But the code 'var firstChild = new parentObj.childObj;' produces the error 'parent.childObjis not a constructor'.

Thus, you can see I'm missing the point - can anyone point me in the right direction?

[Rakuli]

I'm sorry, maybe because I'm tired, can you explaint what you mean in a bit more detail?

To create an object that has children you could use something like

Code: Select all

 
function parentObject (objectId)
{
    this.id = objectId;
    this.children = new Array();
}
 
parentObject.prototype.createChild = function ()
{
    this.children[this.children.length+1] = new childObject(this);
    alert('Child object number ' + this.children.length + ' created!');
}
 
function childObject (parentObj)
{
     this._parent = parentObj;
     this.childId = this._parent.childreb.length + 2;
}
 
var parent = new parentObject('theParent');
 
parentObject.createChild();parentObject.createdChild();parentObject.createChild();