Store selector as value in an NSDictionary

Question

Is there a way to store a selector in an NSDictionary, without storing it as an NSString?

Answer 1

SEL is just a pointer, which you could store in an NSValue:

NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys: 
                       [NSValue valueWithPointer:@selector(foo)], @"foo",
                       nil];

To get the selector back, you can use:

SEL aSel = [[dict objectForKey:@"foo"] pointerValue];

Answer 2

An alternative to Georg's solution would be to convert the selector into an NSString before storing it the NSDictionary:

NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys: 
                      NSStringFromSelector(@selector(foo)), @"foo",
                      nil];

SEL selector = NSSelectorFromString([dict objectForKey:@"foo"]);

This technique, though uses more memory, gives you the ability to serialize the entire NSDictionary as a string via libraries like JSONKit.

Answer 3

An NSDictionary is really just a CFDictionary that retains and releases all keys and values. If you create a CFDictionary directly, you can set it up to not retain and release values. You can typecast a CFDictionaryRef to an NSDictionary * and vice versa.