Re: isKindOf: - GSObjCIsKindOf

[Marko Mikulicic]

Pascal Bourguignon wrote:
> Marko Mikulicic <mikulici@die.supsi.ch> wrote:
>
> > Hello,
> >
> > Is there a way, knowing the name of two classes, test for
> > the isKindOf relation without istantiating the receiver object:
> >
> > I have noticed that those methods in NSObject are defined so:
> >
> >
> > - (BOOL) isKindOf: (Class)aClassObject
> > {
> >   return [self isKindOfClass: aClassObject];
> > }
> >
> > + (BOOL) isKindOfClass: (Class)aClass
> > {
> >   if (aClass == [NSObject class])
> >     return YES;
> >   return NO;
> > }
> > - (BOOL) isKindOfClass: (Class)aClass
> > {
> >   Class class = GSObjCClass(self);
> >
> >   return GSObjCIsKindOf(class, aClass);
> > }
>
> As you can see, there is  a class method named isKindOfClass:. You can
> send this message to a class.  On another hand, all classes are always
> instanciated, you don't loose  anything invoking them, meaning that if
> for  syntactic reason  you need  to write  [MyClass class]  instead of
> MyClass, there's no downside (AFAIK).
>
>          [MyFirstClass isKindOfClass:MySecondClass]

That doesn't work!

assert(GSObjCIsKindOf(NSClassFromString(@"ICalendarDate")
                           ,
                             NSClassFromString(@"NSCalendarDate")));

assert([NSClassFromString(@"ICalendarDate")
                           isKindOfClass:
                             NSClassFromString(@"NSCalendarDate")]);

fails the second assertions.
It seems that the class method +isKindOfClass: has precedence over the
instance method -isKindOfClass: defined in NSObject (an thus inherited 
by every class object).
 The +isKindOfClass: is defined with the == operator and NSObject.
Is this correct ? Shouldn't it return GSObjCIsKindOf(self,aClass) ?

(What should be the result of GSObjCClass(aClass) ?
I have heard something about fixing that in gcc 3.0.1...)

Metaclasses where are you ? :-)



>  
> If you only have the class name  at run time stored in a NSString, you
> can use  the function NSClassFromString (found  in NSObjCRuntime.h) to
> get the class with the given name.
>
>     Class Class1=NSClassFromString(@"MyFirstClass");
>     Class Class2=NSClassFromString(@"MySecondClass");
>     if((Class1!=nil)&&(Class2!=nil)){
>         return([Class1 isKindOfClass:Class2]);
>     }else{
>         return(NO);
>     }
Thanks, I was using NSBundle, but probabliy this is much faster.

Is NSBundle mainBundle classNamed: just slower or it has
a different class searching semantics ?

(Currently I have this objects linked in)

Marko