Hi,
I hadn't thought of __defineSetter__ and __lookupSetter__ but you're
probably right, coding Object.watch in terms of those two methods
shouldn't be a problem. I'll give it a try and post the result to the
mailing-list for those who could be interested.
Thanks for the helpful response.
Matthieu
On Jan 13, 5:15 pm, "David P. Caldwell" <[EMAIL PROTECTED]> wrote:
> On Jan 13, 3:20 pm, Matthieu Riou <[EMAIL PROTECTED]> wrote:
>
> > I was wondering if anybody had thought of implementing Object.watch in
> > Rhino. It's non-standard but pretty convenient, given that there's no
> > way to override '=' in JS and already exists in SpiderMonkey:
>
> I am pretty sure you can do everything you can do with watch with
> __defineSetter__ and __lookupSetter__.
>
> In fact, it might even be possible to implement watch in script code
> in terms of __defineSetter__. I have a method that allows you to
> deprecate a property (and basically execute an arbitrary callback any
> time the property is accessed, which is why I bring it up) using only
> the getter/setter APIs. (I've pasted the code below -- not sure if it
> works on all cases but I haven't found any that it doesn't.)
>
> I do not have an opinion on your original question -- whether to
> implement watch. At least not yet.
>
> ==sample code==
> if (typeof(object[property]) == "function") {
> var deprecateFunction = function(f) {
> return function() {
> warning({ target: object, name: property, call:
> arguments, reason:
> reason });
> // TODO Add regression to cover previous
> mistake of not returning
> this value (but invoking and then returning
> // undefined)
> return f.apply(this,arguments);
> }
> }
> object[property] = deprecateFunction(object[property]);
> return;
>
> }
>
> // If object has neither getter nor setter, we create both with
> versions that cooperate with one another
> // If object has custom getter and/or custom setter, we overwrite both
> with versions that wrap them with warnings
> if (!object.__lookupGetter__(property) && !
> object.__lookupSetter__(property)) {
> var values = new function() {
> var value = object[property];
>
> this.set = function(v) {
> warning({ target: object, name: property, set: v,
> reason:
> reason });
> value = v;
> }
>
> this.get = function() {
> warning({ target: object, name: property, get: value,
> reason:
> reason });
> return value;
> }
> }
> object.__defineGetter__(property,values.get);
> object.__defineSetter__(property,values.set);} else {
>
> var wrapSetter = function(f) {
> return function(value) {
> warning({ target: object, name: property, set: value,
> reason:
> reason });
> if (f) {
> f.apply(this, [ value ]);
> }
> }
> }
>
> var wrapGetter = function(f) {
> return function() {
> var rv;
> if (f) {
> rv = f.apply(this, []);
> }
> warning({ target: object, name: property, get: rv,
> reason:
> reason });
> return rv;
> }
> }
>
> object.__defineGetter__(property,wrapGetter(object.__lookupGetter__(property)));
>
> object.__defineSetter__(property,wrapSetter(object.__lookupSetter__(property)));}
>
> ==end sample code==
>
> -- David P. Caldwellhttp://www.inonit.com/
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