Re: [Dynapi-Dev] An easy way to Subclass/Overwrite functions

[Benoit M. <mar...@ma...>]

This is a very good idea. See bellow my feedback

On Friday, April 4, 2003, at 07:03  AM, Raymond Irving wrote:

> Hi,
>
>
> I've been thinking about creating an easier way to
> subclass/overwrite methods:
>
> DynObject.prototype.subclass = function(n,fn){
> 	if(!this._sbCls) this._sbCls=1;
> 	var om = '_sbMethod'+(this._sbCls++); // old method
>
> eval('fn='+(fn+'').replace(/\~subclass\(/g,'this.'+om+'('));
> 	this[om]=this[n];
> 	this[n]=fn;
> };
>
> Usage:
>
>
> MyWidget.prototype.subclass('setSize',function(w,h){
> 	~subclass(w,h); // call old setSize method;
> 	// some code here
> });
>
> The above would subclass setSize() with the new
> function. The ~subclass() function will allow you to
> call the old/orginal setSize() function

I would prefer
I  prefer the syntax super.setSize(w,h).

What about adding

DynAPIObject.prototype.overwrite = function(sC,n) {
     var c = this.frame[sC];
     var superMethod = c.prototype._superPrototype[n];
     var capitalized = n.charAt(0).toUpperCase() + 
n.substring(1,n.length);
     var	superMethodOverridename = 'super'+ capitalized;
     if(superMethod && !c.prototype[superMethodOverridename]) {
         c.prototype[superMethodOverridename] = superMethod;
     }
};

and in the class you want to overwrite:
p.setSize = function(width,height) {
	this.superSetSize (widt h,height);
	//Then do your stuff
}
dynapi.overwrite('EventObject','setSize');//which basically does 
p.superSetSize = mySuperClass.prototype.setSize


that way it's in the same fashin as the setPrototype() ?
It's "clean" in the sense that it's important to overrides only the 
implementation defined is in your super class, guaranteeing a correct 
overriding if different subclasses overrides the same method multiple 
time. In javascript, it's easy to directly  get the implementation of 
an of your ascendant, and bypass some !

Benoit

>
> It's similar to:
>
> MyWidget.prototype._oldSetSize =
> DynLayer.prototype.setSize;
> MyWidget.prototype.setSize =
> function('setSize',function(w,h){
> 	this.oldSetSize(w,h); // call old setSize method;
> 	// some code here
> });
>
>
> Is the term "subclass" correct or should we term it as
> "overwrite"?
We should use overwrite, it's the appropriate term in OO terminology 
when a subclass modify an inherited method.

Benoit

>
> Any comments?
>
> --
> Raymond Irving
>
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