Subj : Re: about defining object...
To   : netscape.public.mozilla.jseng
From : celleris@naver.com (Youngsun Jeong)
Date : Wed Oct 01 2003 09:50 pm

Brendan Eich <brendan@meer.net> wrote in message news:<3F7B0C64.2090008@meer.net>...
> Youngsun Jeong wrote:
> 
> >And I write a native constructor:
> >
> >//native constructor
> >static JSBool
> >MyObj(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval
> >*rval)
> >{
> >    if(argc == 0)
> >    {
> >        obj = NULL;
> >  
> >
> 
> It seems better for your constructor to make a new object of your class, 
> even when called with no arguments.
> 
> >    }
> >    else
> >    {
> >        if(!js_ValueToObject(cx, argv[0], &obj))
> >            return JS_FALSE;
> >    }
> >  
> >
> 
> This makes your constructor, whether called via new or not, convert its 
> argument to an object and return that.  That's wrong.  If a script calls 
> 'new myobject(42)', you should construct an object of my_class and give 
> it an age, perhaps 42.
> 
> In other words, you should call JS_IsConstructing(cx) (see below for 
> more) early, and if not constructing (if not called via operator new), 
> then consider doing an argument conversion.

I modified that : 
           }
           else
           {
              if(!JS_IsConstructing(cx))
              {
                  if(!js_ValueToObject(cx, argv[0], &obj))
                      return JS_FALSE;
              }
           }

> >    if(!obj)
> >    {
> >        JS_ASSERT(!argc || JSVAL_IS_NULL(argv[0]) ||
> >JSVAL_IS_VOID(argv[0]));
> >        if (cx->fp->flags & JSFRAME_CONSTRUCTING)
> >            return JS_TRUE;
> >  
> >
> 
> Again, you should *not* include "jscntxt.h" and use cx->fp or any other 
> member.  Use JS_IsConstructing(cx).

Yes, I modified that.
 if (cx->fp->flags & JSFRAME_CONSTRUCTING) 
   => if(JS_IsConstructing(cx))

> >        obj = js_NewObject(cx, &my_class, NULL, NULL);
> >       
> >        if (!obj)
> >            return JS_FALSE;
> >  
> >
> 
> Here you can JS_SetPrivate to associate an age with the new obj.  
> Perhaps the age can come from argv[0].
> 
 
 obj = js_NewObject(cx, &my_class, NULL, NULL);
  
 if (!obj)
      return JS_FALSE;
 JS_SetPrivate(cx, obj, argv[0]); Is that right?

And I tested my code. See below ;
 testscript : 
    function sumage(age)
    {
        var myage = age.plusAge(10); //myage = age + 10
        return myage;
    }
 "age" value is integer.
But, it's not working. I got the error message "TypeError: age.plusAge
is not a function".

What is wrong? How "age" value is passed to function "plusAge()"
*without* constructing myobject(that is "var myobj = new myobject();")
*on the script*?

.