doubts about rooting a callback function

[Ricardo Quesada]

Hi List,


I am working on adding Javascript support to cocos2d-iphone (a popular
Objective-C engine).
I created an script that parses Objective-C code and generates glue code
for Spidermonkey.
So far, it is working OK...

...but I have a doubt regarding how to handle Javascript callback functions
inside SpiderMonkey. In particular, I do not know how what is the best
strategy to "root" "orphan" functions.
* should I add it as a slot of "this" ?
* should I add it as a property of this ?
* If I add it in the "root", when should I remove it ?

Thank you,

Ricardo

Example:

// When the callback is an "orphan" function, and if the garbage collector
is
// called, then it will crash.
item.setCallback( function( sender )
{
cc.log("Clicked me from" + sender );
} );


// If the function was previously assigned to a property, then it will work
OK.
item.setCalback( item.callback );


On the "C" code, I have the following:

typedef void (^js_block)(id sender);

js_block jsval_to_block( JSContext *cx, jsval vp, JSObject *jsthis )

{

NSCAssert( JS_ValueToFunction(cx, vp ), @"Should be a function");


// HOW DO I "ROOT" vp ? Should I 'clone' it. I cannot use "vp" since it is
in the stack.

// Is there a way to know if "vp" is an "orphan" function ?

// If I "root" it, what is the best strategy to "unroot" it ?

// Is it a good practice to add it as an "slot" of the object ?


js_block block = ^(id sender) {


jsval rval;

JSObject *jsobj = get_or_create_jsobject_from_realobj( cx, sender );

jsval val = OBJECT_TO_JSVAL(jsobj);


// Will crash here if "vp" is orphan, and the GC is called before this

JS_CallFunctionValue(cx, jsthis, vp, 1, &val, &rval);

};

return [[block copy] autorelease];

}


JSBool JSPROXY_CCMenuItem_itemWithBlock__static(JSContext *cx, uint32_targc,
jsval *vp) {


...

jsval *argvp = JS_ARGV(cx,vp);

js_block arg0;


arg0 = jsval_to_block( cx, *argvp++, JS_THIS_OBJECT(cx, vp) );


...


return JS_TRUE;

}