Javascript object array - destruction by suicide

Question

I have an array of lightweight objects, each of which is the Subject of an Observer pattern. To conserve memory, when the Subject is no longer observed, i want to release the object's resources and make it remove itself from the parent array. So how do I ask either the parent object or the Array itself to splice the item, from code within the item itself? What I came up with is something like:

var parentObj = {
   items : [],
   addItem : function () {
       var newItem = new ItemObj;
       items.push(newItem);
   },
   removeItem : function (item) {
       for (var i = this.items.length; i--; i < 0) {
            if (this.items[i] == item) {
                this.items.splice(i, 1);
                return;
            }
        }
    }
};

function ItemObj() {}
ItemObj.prototype = {
   observers : [],
   observerRemove : function(observer){
       //find observer in observers array and splice it out
           ....
       //now here's the part where it gets tricky
       if (this.observers.length == 0) {
          parentObj.removeItem(this);
       }
   },
   //observerAdd.... etc
 };

Which works, but only because parentObj is a named variable, if it were a class, it would not be so easy. Also, this seems a little clumsy. It would be nice if ItemObj could have some reference to it's parent Array object, but I can't find that. Any suggestions? Perhaps passing a reference from parentObj of itself to each ItemObj? as in

              newItem.parentArray = this.items;

when creating the itemObj? Again, seems clumsy.

keslert · Accepted Answer · 2013-10-16 19:16:26Z

2

Why not just add a reference to the parent in the item class.

var parentObj = {
   items : [],
   addItem : function () {
       var newItem = new ItemObj;
       newItem.parent = this; // set the parent here
       items.push(newItem);
   },
   removeItem : function (item) {
       for (var i = this.items.length; i--; i < 0) {
            if (this.items[i] == item) {
                this.items.splice(i, 1);
                return;
            }
        }
    }
};

function ItemObj() {}
ItemObj.prototype = {
   parent: null,
   observers : [],
   observerRemove : function(observer){
       //find observer in observers array and splice it out
           ....
       //now here's the part where it gets tricky
       if (this.observers.length == 0) {
          this.parent.removeItem(this); // use the parent here
       }
   },
   //observerAdd.... etc
 };

edited Oct 16, 2013 at 19:16

answered Oct 16, 2013 at 16:48

keslert

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2 Comments

grape_mao Over a year ago

Should it be this.parent.removeItem(this);?

Peter Brand Over a year ago

Ah, that seems so simple now that I look at it. Thanks guys.

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