NSClassFromString works for string literals, returns nil for constructed strings

Question

I am trying to create an instance of a type based on another type passed into a method. I find that NSClassFromString works just fine if used with a string literal, as in

id instance = [[NSClassFromString(@"TheNameOfTheClassIWant") alloc] init];

but if I construct the string with something like

NSString *inClassName = [[protoInstance class] description];
NSString *outClassName = [inClassName stringByAppendingFormat:@"IWant"];
id instance = [[NSClassFromString(outClassName) alloc] init];

that instance is nil. Does NSClassFromString only work with literals? Is something happening at compile time to make NSClassFromString work?

Answer 1

i've never had a problem using this call (granted, i have only needed it a few times).

you've:

• verified that outClassName is letter perfect (case-sensitive)?
• verified that the bundle/class has loaded? you are able to alloc/init a class using the standard approach?
• verified the output of NSClassFromString' - just to ensure thatinit` isn't returning 0 (as one example)

Answer 2

The only thing I can think of is [Class description] is dubious. Use NSStringFromClass to be sure you got what you want?