Objective C: how to check if variable is NSArray or NSMutableArray

Here's my little test code, with its results below. It demonstrates the technique of verifying mutability of Foundation collection objects.

Take note that the mutable versions (e.g. NSMutableArray) inherit from the immutable ones (NSArray) and so testing for the class needs attention.

Also the test for implementation of mutable-only methods seems to work find, but may be a little slower than the test of class.

In any way - AVOID using @try and @catch to attempt mutating immutable objects, according to Apple docs these should not be used in deployment code- since exceptions cause stack unrolling which is specifically costly and also prevents and voids lots of optimizations.

id arr1 = [NSArray arrayWithObjects:@"Motti",@"name",@55, @"age", nil];
id arr2 = [NSMutableArray arrayWithObjects:@"Motti",@"name",@55, @"age", nil];

NSLog (@"arr1 isKindOfClass NSArray:%@, NSMutableArray:%@", [arr1 isKindOfClass:[NSArray class]] ? @"YES" : @"NO", [arr1 isKindOfClass:[NSMutableArray class]] ? @"YES" : @"NO");
NSLog (@"arr2 isKindOfClass NSArray:%@, NSMutableArray:%@", [arr2 isKindOfClass:[NSArray class]] ? @"YES" : @"NO", [arr2 isKindOfClass:[NSMutableArray class]] ? @"YES" : @"NO");

NSLog (@"arr1 implements insertObject:atIndex:%@", [arr1 respondsToSelector: @selector(insertObject:atIndex:)] ? @"YES" : @"NO");
NSLog (@"arr2 implements insertObject:atIndex:%@", [arr2 respondsToSelector: @selector(insertObject:atIndex:)] ? @"YES" : @"NO");

id dict1 = [NSDictionary dictionaryWithObjectsAndKeys:@"Motti",@"name",@55, @"age", nil];
id dict2 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"Motti",@"name",@55, @"age", nil];

NSLog (@"dict1 isKindOfClass NSDictoinary:%@, NSMutableDictionary:%@", [dict1 isKindOfClass:[NSDictionary class]] ? @"YES" : @"NO", [dict1 isKindOfClass:[NSMutableDictionary class]] ? @"YES" : @"NO");
NSLog (@"dict2 isKindOfClass NSDictoinary:%@, NSMutableDictionary:%@", [dict2 isKindOfClass:[NSDictionary class]] ? @"YES" : @"NO", [dict2 isKindOfClass:[NSMutableDictionary class]] ? @"YES" : @"NO");

NSLog (@"dict1 implements setObject:forKey:%@", [dict1 respondsToSelector: @selector(setObject:forKey:)] ? @"YES" : @"NO");
NSLog (@"dict2 implements setObject:forKey:%@", [dict2 respondsToSelector: @selector(setObject:forKey:)] ? @"YES" : @"NO");

and the results printout:

14:30:42.2683 Test[381:286] arr1 isKindOfClass NSArray:YES, NSMutableArray:NO
14:30:42.2683 Test[381:286] arr2 isKindOfClass NSArray:YES, NSMutableArray:YES
14:30:42.2684 Test[381:286] arr1 implements insertObject:atIndex:NO
14:30:42.2684 Test[381:286] arr2 implements insertObject:atIndex:YES
14:30:42.2684 Test[381:286] dict1 isKindOfClass NSDictoinary:YES, NSMutableDictionary:NO
14:30:42.2685 Test[381:286] dict2 isKindOfClass NSDictoinary:YES, NSMutableDictionary:YES
14:30:42.2686 Test[381:286] dict1 implements setObject:forKey:NO
14:30:42.2687 Test[381:286] dict2 implements setObject:forKey:YES