NSDictionary not key value coding-compliant for the key Test

Question

I'm trying to use NSDictionary in a way that I can store NSArrays in it, but I can't even get it working for strings.

_times = [[NSDictionary alloc] init];
NSString *test = @"Test";
[_times setValue:@"testing" forKey:test];
NSLog(@"%@",[_times objectForKey:test]);

For the code above, I get the error message
Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<__NSDictionaryI 0x8b86540> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key Test.'

Why would an NSString * not work as a key? In fact, that's precisely what the method calls for.

Answer 1

NSDictionary is immutable, so you can't set value to it.
use NSMutableDictionary

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

I am including @Martin's comment here

In addition: Use setObject:forKey to set dictionary values. setValue:forKey is only needed for "Key-Value Coding" magic. setObject:forKey would also give a better error message if applied to an immutable dictionary.

Answer 2

Also, for dictionaries, KVC is an inefficient way to set key/value pairs. Better to use the NSMutableDictionary method setObject:forKey: