Re: Array property of custom object

On Tuesday, May 3, 2016 at 6:12:03 PM UTC+3, Boris Zbarsky wrote:
> On 5/3/16 3:25 AM, Mihai Dobrescu wrote:
> > ....well, I did not say js::proxies.
> 
> OK, let's not use "proxy" without clearly stating which of the many 
> meanings we're using, because that way lies only frustration.
> 
> > 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?
> 
> Let me try to state this more clearly.
> 
> If you want |var x = obj.arr| to return an object that will call code 
> you control when x[5] is read or set, and the precise set of property 
> names for which you want your code to be called is not known up front, 
> then obj.arr needs to be a js::Proxy.  The proxy handler's methods are 
> what will get called when x[5] is read or set.
> 
> If you do know the precise set of property names you care about up front 
> (e.g. you want your code to be called for x[N] where 0 <= N < 100, but 
> don't want your code called when N is 101), then you can get away with 
> defining a bunch of accessor properties on obj.arr instead of using a 
> js::Proxy.  Obviously for large N this could have deleterious memory 
> effects.
> 
> Does that help?
> 
> -Boris

Well, I think I was right, though. I did used all the juice of SpiderMonkey similarly to a js::proxy, as I had used the private data functionality and customized all ops as far as I could... although I did not use the js::proxy itself.

Now, I have the question how could I use js::proxy to attain my goal, being aware of its drawbacks. I'm sure it involves memory fragmentation and cpu load.
Will it make possible to simply iterate too?