Re: Array property of custom object

On Tuesday, May 3, 2016 at 10:25:53 AM UTC+3, Mihai Dobrescu wrote:
> On Tuesday, May 3, 2016 at 5:01:42 AM UTC+3, Boris Zbarsky wrote:
> > On 5/2/16 4:30 PM, Mihai Dobrescu wrote:
> > > I need to e able to replace array elements, probably I will need to add/remove elements too
> > 
> > OK. I have a hard time reconciling adding elements that with your claim 
> > that your backing storage is a constant-sized array, but I assume you 
> > know what you're doing.
> > 
> > > Aren't all the JS objects containing private data proxies (the one with the JSCLASS_HAS_PRIVATE flag)?
> > 
> > Not at all.
> > 
> > -Boris
> 
> ...well, I did not say js::proxies.
> 
> I could try to post a sample of my approach for a property getter to be passed to the JS_PSGS macro (extremely simplified as it is template based solution):
> 
> template<typename jsType, typename jsPropertyType, typename jsPropertyType::PrivateType PrivateType::*Property>
>     static bool GetProperty(JSContext *cx, unsigned argc, JS::Value *vp)
>     {
>         JS::CallArgs args = CallArgsFromVp(argc, vp);
> 
>         PrivateType* data = (PrivateType*)(JS_GetPrivate(&args.thisv().toObject()));
> 
>         if (!data)
>             return false; // whatever...
> 
>         JSObject *obj = JS_NewObject(cx, &jsDataClass<jsPropertyType>::fClass);
> 
>         JS_SetPrivate(obj, new jsPropertyType::PrivateType(data->*Property));
> 
>         args.rval().setObject(*obj);
> 
>         return true;
>     }
> 
> where jsPropertyType is a wrapper for the property's type. jsType is the property owner wrapper object. All of these have a PrivateType typedef for the wrapped C type. It should be pretty clear for a person with SpiderMonkey knowledge. 
> 
> It is my approach I could find for embedding API's types.
> 
> I could ask also, how do you know should be done? For any of these, simple and array properties. If you do it from scratch, what is your approach?

And I have to apologize for forgetting to say what is my issue: considering this approach, I fail to find a way to pass the index of the array element to access for some operation.