Cocoa/Objective-C - Verify if a key exist on a NSDictionary [duplicate]

Question

How do I verify if a key exists on a NSDictionary?

I know how to verify if it has some content, but I want to very if it is there, because it's dynamic and I have to prevent it. Like in some cases it could happen to have a key with the "name" and is value, but in another cases it could happen that this pair of value don't exists.

Answer 1

The simplest way is:

[dictionary objectForKey:@"key"] != nil

as dictionaries return nil for non-existant keys (and you cannot therefore store a nil in a dictionary, for that you use NSNull).

Edit: Answer to comment on Bradley's answer

You further ask:

Is there a way to verify if this: [[[contactDetailsDictionary objectForKey:@"professional"] objectForKey:@"CurrentJob"] objectForKey:@"Role"] exists? Not a single key, because is a really giant dictionary, so it could exist in another category.

In Objective-C you can send a message to nil, it is not an error and returns nil, so expanding the simple method above you just write:

[[[contactDetailsDictionary objectForKey:@"professional"] 
                              objectForKey:@"CurrentJob"] 
                                objectForKey:@"Role"] != nil

as if any part of the key-sequence doesn't exist the LHS returns nil

Answer 2

NSDictionary returns all of the keys as an NSArray and then use containsObject on the array.

NSDictionary* dictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"object", @"key"];
if ([[dictionary allKeys] containsObject:@"key"]) {
  NSLog(@"'key' exists.");
}