I agree, that method exists, not quite sure what your question is though.
Depends what you want to do with introspection. If you want to ensure a class
responds to allObjects and you expect if it does it returns an NSArray, that
still works in this case, if you are trying to work out what an object is by
checking what methods it supports, it's fragile and is going to get broken
however hard you try and that is an unfortunate fact. If it's all your code you
can limit that, if you're writing a library you are at the mercy of any
category anyone added to anything anywhere.
I do personally feel that somewhere around the time class clusters arrived on
the scene, a method isKindOfClassReally should have arrived too which hides the
implementation from the interface
On 24 Oct, 2013, at 10:19 pm, Jerry Krinock <je...@ieee.org> wrote:
>
> Starting somewhere after OS X 10.6, NSArray instances respond to the NSSet
> method -allObjects. I can’t find any documentation of this. Also, it is not
> declared in the header NSArray.h
>
> Although it does what you’d expect, returning a copy of self, this can lead
> to some interesting bugs, particularly when running in 10.6 after testing in
> a current system :( And in some cases one may want to reconsider the usual
> strategy of preferring -respondsToSelector: instead of -isKindOfClass: for
> introspection.
>
> Just to make sure that I hadn’t implemented -allObjects in a forgotten
> category, I ran the following test in a new little Command-Line Tool project
> and target…
>
> #import <Foundation/Foundation.h>
>
> void Check(Class class) {
> BOOL doesRespond = [class
> instancesRespondToSelector:@selector(allObjects)] ;
> NSLog(@"%hhd for %@", doesRespond, NSStringFromClass(class)) ;
> }
>
> int main(int argc, const char * argv[]) {
>
> @autoreleasepool {
> Check([NSSet class]) ;
> Check([NSMutableSet class]) ;
> Check([NSArray class]) ;
> Check([NSMutableArray class]) ;
> Check([NSString class]) ;
> Check([NSMutableString class]) ;
>
> NSObject* a = [NSArray arrayWithObjects:
> @"a", @"b", @"c", nil] ;
>
> SEL selector = @selector(allObjects) ;
> if ([a respondsToSelector:selector]) {
> NSLog(@"%@ %p DOES respond to allObjects.", [a className], a) ;
> NSSet* s = [a performSelector:selector] ;
> NSLog(@"allObjects returned %@ %p: %@", [s className], s, s) ;
> }
> else {
> NSLog(@"%@ does NOT respond to allObjects.", [a className]) ;
> }
> }
>
> return 0 ;
> }
>
> *** Result, in 10.9:
>
> 2013-10-24 07:02:19.752 Junk[27092:303] 1 for NSSet
> 2013-10-24 07:02:19.755 Junk[27092:303] 1 for NSMutableSet
> 2013-10-24 07:02:19.756 Junk[27092:303] 1 for NSArray
> 2013-10-24 07:02:19.756 Junk[27092:303] 1 for NSMutableArray
> 2013-10-24 07:02:19.757 Junk[27092:303] 0 for NSString
> 2013-10-24 07:02:19.757 Junk[27092:303] 0 for NSMutableString
> 2013-10-24 07:02:19.758 Junk[27092:303] __NSArrayI 0x100400d10 DOES respond
> to allObjects.
> 2013-10-24 07:02:19.759 Junk[27092:303] allObjects returned __NSArrayI
> 0x100300d90: (
> a,
> b,
> c
> )
> Program ended with exit code: 0
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