Question

In my code, I’m dynamically creating classes, and trying to store them in a NSMutableDictionary:

NSMutableDictionary* classDict = [ [ NSMutableDictionary alloc ] init ];  

...start loop

Class customClass = objc_allocateClassPair( [ TestClass class ], className, 0 );

[ classDict setObject:customClass forKey:name ]

...end loop

...add methods to certain classes within the dict

...register classes with objective c

When I run the code, a “EXC_BAD_ACCESS” is thrown when it’s trying to add the Class to the dictionary. Is there a way to get around this? That is, is there a way to add a unregistered Class to a NSMutableDictionary? The alternative solution is to use a std:map data structure instead.

Thanks in advance.

Answer 1

To answer the actual question: adding a Class object to a dictionary is simple:

[dict setObject:[TestClass class] forKey:@"key"];

And I do so often, without any issue. However, you seem to want to add an unfinished class object. The documentation states:

When you are done building the class, call objc_registerClassPair. The
new class is now ready for use.

So maybe your Class object is not “ready for use” yet?

update after some tests:

you need to call objc_registerClassPair in order to use Class as an actual object. Calling retain before this time will lead to an EXC_BAD_ACCESS.

If you want to create classes in a loop, and register them in a later stage, just box the pointers, using:

[classDict setObject:[NSValue valueWithPointer:customClass] forKey:name];

simply unbox them using Class customClass = [value pointerValue];. After registering you can of course use the Class objects as usual.