Subj : Re: Creating Class Globally
To   : netscape.public.mozilla.jseng
From : Brian Genisio
Date : Tue Apr 20 2004 02:50 pm

Brendan Eich wrote:

> Brian Genisio wrote:
> 
>> Hey all,
>>
>> Is there any way to create a Class for use in all contexts?
>>
>> I have a program running with many threads, and many contexts per 
>> thread.  In addition, I have about 40 classes I need to initialize 
>> using JS_InitClass.  I also have a context in the main thread that is 
>> alive as long as any thread is alive.
> 
> 
> 
> A context is for running scripts, but it is not the same thing as a 
> global object.  You need a global object as the scope chain for global 
> code, to hold the standard classes (Object, Date, etc.) plus your own. 
> How many global objects do you have?  If you have one per context, then 
> you do need to use JS_InitClass for each.
> 
> 
>> It seems like a waste to call InitClass for _every_ context.
> 
> 
> 
> You mean "for every global object."
> 
> But if it were a waste, you could avoid it and leave some global objects 
> without standard or custom class constructors, prototypes, etc.  How 
> then would scripts work with those global objects?
> 
> The approach of using JS_SealObject on a root context's standard 
> objects, before any other objects reference them, can work, but it is 
> not compatible with ECMA-262, or with JS as many scripts use JS.  Once 
> sealed, the object graph can't be changed at all, so you can't add 
> String.prototype.sub to create a custom substring (or subscript, 
> whatever) method.
> 
> 
>> Is there a way to use the classes created in the main context?  I 
>> tried this, but when I try to construct an object with 
>> JS_ConstructObjectWithArguments, it returns NULL for the object.
> 
> 
> 
> I have no idea what you did -- can you say more, or better, show code?
> 
> 
>> Do I need to do anything to tell the context to use classes defined in 
>> a different context?
> 
> 
> 
> Instead of worrying about pre-creating standard and/or custom classes, 
> look into using JS_ResolveStandardClass and the same technique for your 
> own custom classes.  See js.c.
> 
> /be

Yes, I understand now.  It is necessary for me to init the classes for 
each global object, which is associated with each concept.  I reworked 
my code, and it works now.

Thanks,
Brian

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