Question

I am coding a fairly complex system that uses a lot of metadata to manage dynamic objects. I am using various objective-c runtime features. I want to add stuff to mutable dictionaries which are properties within various classes. I want to do this where I know the class type and I know the property name, but I don’t want to ‘hard code’ the assignment. If I hard-coded it I could do this:

[[(myknownclass*)localClassObjectInstance knownDictionary] setObject:value forKey:key];

but what I want to do is something like this:

[[unknownClassObjectInstance {aStringContainingTheDictionaryName}] setObject:value forKey:key];

How can I reference the mutable dictionary property when I only have the name of the property at runtime?

Answer 1

You can use -valueForKey: to run the method:

[(NSMutableDictionary*)[inst valueForKey:@"whateverMethodName"] setObject:o forKey:k];

Or alternatively, you can use performSelector:

SEL dictGetter = NSSelectorFromString(@"whateverMethodName");
NSMutableDictionary* dict = [inst performSelector:dictGetter];
[dict setObject:o forKey:k];