Now look what I've gone and started.. :-)
----- Original Message -----
From: "Tuomas Huhtanen" <[EMAIL PROTECTED]>
To: "Dynapi-Help@Lists. Sourceforge. Net"
<[EMAIL PROTECTED]>
Sent: Tuesday, September 25, 2001 4:45 AM
Subject: RE: [Dynapi-Help] loading inline layers
> > > > It would be nice if we could clone layers :)
>
> I would recommend doing it with a similar scheme as in java. Define an
> "interface" cloneable, which contains a method called clone(). If an
object
> has an method called clone(), that will be run when cloning. Otherwise the
> old object reference is kept.
>
> The general solution which work for most of the objects looks something
> like:
>
> function clone() {
> var oNew = new Object();
> for (var i in this) {
> //If i is cloneable, clone it
> if (typeof(this[i]) == 'object' && this[i]['clone']!=null){
> oNew[i] = this[i].clone();
> }
> //Otherwise keep the old reference
> else{
> oNew[i] = this[i];
> }
> }
> return oNew;
> }
>
> I have not tested that code, but the idea should be clear. The previous
code
> has clearly a problem when cloning other than strictly hierarchical object
> structures. If we try to clone an object which has an circular reference
> (a.b == b && b.a == a), the result is not what we want. (A system crash,
> namely) So we need to define individual clone methods for those
complicated
> objects.
>
> Here is an example for something that imitates a twoway linked list:
>
> function Node(left, right, content){
> this.left = left;
> this.right = right;
> this.content = content;
> }
>
> Node.prototype.clone = function(){
> var oNew = new Object();
> oNew.left = this.left; //Take the "old" reference, do not clone
> oNew.right = this.right.clone(); //clone this one
> if( typeof(this.content)=='object && this.content.clone!=null){
> oNew.content = this.content.clone(); //Clone it if its cloneable
> }
> else{
> oNew.content = this.content;
> }
> }
>
> This version of clone assumes that the clone is always started from the
> leftmost node.
>
> Note that you can still use the first method for the most of the objects,
as
> long as you remember to add the specific methods for the objects that need
> them. You could even say that Object.prototype.clone = [the first method],
> but then you need to take extra special care of the circular references.
>
> This example here is not complete, but it should give a clear enogh
picture
> what needs to be done to provide means to clone objects.
>
> --
> Tuomas Huhtanen
>
>
>
>
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