Question

Possible Duplicate:
How to add to an NSDictionary

When I do that :

NSDictionary *dic = [NSDictionary dictionary];
[dic setValue:@"nvjd" forKey:@"name"];

my app just crash. I don’t understand why. How should I add a string in a dictionary ?

Answer 1

You need to make your dictionary mutable, otherwise it would not respond to the setValue:forKey: selector:

NSMutableDictionary *dic = [NSMutableDictionary dictionary];

This is a common pattern in cocoa: you often see classes declared in pairs: NSArray/NSMutableArray, NSSet/NSMutableSet, NSString/NSMutableString, and so on. Mutable version is capable of doing everything that the immutable version can do, but it also supports operations that change its content.