I'm not sure you get exactly what I'm saying as you put class in places
where I'd expect property. For instance:
"
I looked briefly, and it seems like it would be relatively easy to add
an API for adding C getters and setters to a class individually. So,
that seems like a reasonable feature request. "
Replacing class with property is what I'd expect here, i.e., each
property set on an object has it's own getter and setter. Something like:
void
JSObjectSetPropertyWithCallback(ctx,object,propertyName,value,getterFunction,setterFunction,attributres,exception);
Also I'm a little worried about the word "dynamic", these are definitely
static. I have all the functions created, you just have a pointer to
them. If the pointer exist, call it for the value and break out. If it
doesn't, go down the chain. More pseudo code:
void main(...)
{
obj=JSObjectMake(ctx,NULL,NULL);
JSObjectSetPropertyWithCallback(ctx,obj,"red",JSValueMakeNull(),myRedGetter,myRedSetter,attributes,exception);
}
JSValueRef myRedGetter(...ctx...object...exception)
{
return(JSValueMakeNumber(red_value));
}
bool myRedSetter(..ctx..object..value..exception)
{
red_value=JSValueToNumber(ctx,value,exception);
}
Here are the benefits (as I see them):
1) I don't need to define classes for objects; right now, the only
reason I would need to create classes (instead of just passing NULL) is
to setup the getters & setters. This reduces workload and generalizes a
lot of my code
2) The JS engine has already looked up the property by name; with class
based getters/setters, I also have to lookup the property by name. With
property based getters/setters, it's only looked up once and directly
called to me. This should be a big savings win and should be more
simple at the back end (if there's no getter/setter associated with a
property, just skip forward down the chain.)
I'm not sure how this could be anything but faster then class-based.
[>] Brian
Geoffrey Garen wrote:
Hi Brian.
I see what you mean now.
In JavaScriptCore, there's no API for defining C getters and setters
individually. There's an API for associating a set of C getters and
setters with a class, and there's an API for defining a generic
fallback getter and setter for a class.
I looked briefly, and it seems like it would be relatively easy to add
an API for adding C getters and setters to a class individually. So,
that seems like a reasonable feature request.
I'm not sure how important it is to you to be able to add C getters
and setters to objects, as opposed to classes, individually. I think
that would be a trickier API to get right. The main challenge is that
getters and setters of that dynamic nature tend to slow down the
object system. So, we would either want to engineer a way to avoid the
performance cost in most cases, or we would want to design a way to
steer API users away from that particular API in the general case. If
you have a good example of how this feature would be generally useful
to API clients, it's still a reasonable request, though.
Geoff
On Jul 20, 2009, at 10:21 AM, Brian Barnes wrote:
In SpiderMonkey, you can create an object, and that object has a
callback to a getter or a setter in C. You get the name, look it up,
return or set a value. Nitro has that same functionality.
On SpiderMonkey, though, when creating a property, you can also do this:
JS_DefineProperty(context,object,name,value,getter,setter,flags);
Where "getter" and "setter" are direct calls for the property, for
only that property. There's no lookup logic in my code.
So, in pseudo code, at object level, we'd have a single getter:
void getMyObjectValues(.... name ...)
{
if (name == 'red') return(red)
if (name == 'green') return(green)
if (name == 'blue') return(blue)
}
And property level, we'd have 3 getters:
void getMyObjectRed(...)
{
return(red);
}
void getMyObjectGreen(...)
{
return(green);
}
void getMyObjectBlue(...)
{
return(blue);
}
[>] Brian
Geoffrey Garen wrote:
Hi Brian.
I don't understand the distinction you're drawing between "the
property level" and "the object level". Can you explain what those
mean and give an example of each?
Thanks,
Geoff
On Jul 20, 2009, at 9:14 AM, Brian Barnes wrote:
I was getting ready to try the first move from SpiderMonkey to
Nitro, and ran into a large problem. Right now, all my getters and
setters are at the property level. In the documentation I have,
Nitro only seems to put them at the object level. This would force
a huge refactoring of my code (which I'm willing to do if I have
to, I would just like to avoid it as I have hundred or so objects.)
Is my documentation old, did I miss something, or am I stuck? If
I'm stuck, is there any call to have this put into Nitro at some
time in the future?
[>] Brian
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