Function templates versus Object templates in V8

[Prahalad Deshpande]

Hi,

I was reading the Embedders guide on the Wiki and came across the
concept of FunctionTemplates and ObjectTemplates.

Could someone provide an explanation about them annotated with
examples? Somehow I felt that the documentation in the Wiki did not
make the distinction clear.

Basically, when will we want to go for a FunctionTemplate and when do
we use an ObjectTemplate?

Thanks
-Prahalad

[Matthias Ernst]

Maybe http://groups.google.com/group/v8-users/browse_thread/thread/fa1fd963c570ff06/995c427977ebb78b
helps.

Matthias

> Thanks
> -Prahalad
>
> --
> v8-users mailing list
> v8-u...@googlegroups.com
> http://groups.google.com/group/v8-users

[christy]

I have a question can FunctionTemplates be used like an
ObjectTemplate?

In other words it is possible for a FunctionTemplate to do something
like this...

V8FunctionTemplateHandle functionTemplateHandle =
V8FunctionTemplate::New(InternalConstructor, external);
V8ObjectTemplateHandle instanceTemplate = new functionTemplateHandle-
>InstanceTemplate();
V8ObjectHandle instance = instanceTemplate->NewInstance();
instance->SetInternalField(0, external);
global->Set(V8Converter::ToV8String(Name), v8Instance);

Essentially what I want to do is register a single instance of the
Function Template and "hide" the constructor by not registering it in
the context.

Since I'm registering a single instance to the context it seems to me
the instance should behave as if I used an ObjectTemplate.

If this behavior is supported than that would make coding for what I'm
doing easier since I can internally treat all objects being created
from FunctionTemplate.

Thanks.

[Matthias Ernst]

On Tue, Aug 3, 2010 at 12:29 AM, christy <christy...@gmail.com> wrote:
> I have a question can FunctionTemplates be used like an
> ObjectTemplate?
>
> In other words it is possible for a FunctionTemplate to do something
> like this...
>
> V8FunctionTemplateHandle functionTemplateHandle =
> V8FunctionTemplate::New(InternalConstructor, external);
> V8ObjectTemplateHandle instanceTemplate = new functionTemplateHandle-
>>InstanceTemplate();
> V8ObjectHandle instance = instanceTemplate->NewInstance();
> instance->SetInternalField(0, external);
> global->Set(V8Converter::ToV8String(Name), v8Instance);
>
> Essentially what I want to do is register a single instance of the
> Function Template and "hide" the constructor by not registering it in
> the context.

Absolutely. FunctionTemplate#getFunction#newInstance and
FunctionTemplate#getInstanceTemplate#newInstance are equivalent.

But note that the "constructor" property of the object will still be
available to JS code to call.

>
> Since I'm registering a single instance to the context it seems to me
> the instance should behave as if I used an ObjectTemplate.
>
> If this behavior is supported than that would make coding for what I'm
> doing easier since I can internally treat all objects being created
> from FunctionTemplate.
>
> Thanks.
>

[christy]

Matthias,

Thanks for your response. I can live with the constructor property
on the object since if the constructor property is called it will only
return a reference of the same object so there is no harm.. Using
only the FunctionTemplate for what I'm doing makes the code cleaner.

Thanks again.