Re: Array property of custom object

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 t 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?