NSMutableDictionary

NSMutableDictionary Example

+ dictionaryWithCapacity:

Creates and returns a mutable dictionary, initially giving it enough allocated memory to hold a given number of entries.

NSMutableDictionary *dict =  [NSMutableDictionary dictionaryWithCapacity:1];
NSLog(@"%@",dict);

- init

Initializes a newly allocated mutable dictionary.

NSMutableDictionary *dict =  [[NSMutableDictionary alloc] init];        
NSLog(@"%@",dict);

+ dictionaryWithSharedKeySet:

Creates a mutable dictionary which is optimized for dealing with a known set of keys.

id sharedKeySet = [NSDictionary sharedKeySetForKeys:@[@"key1", @"key2"]]; // returns NSSharedKeySet
NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithSharedKeySet:sharedKeySet];
dict[@"key1"] = @"Easy";
dict[@"key2"] = @"Tutorial";
//We can an object thats not in the shared keyset
dict[@"key3"] = @"Website";
NSLog(@"%@",dict);  

OUTPUT

{
    key1 = Eezy;
    key2 = Tutorials;
    key3 = Website;
}

Adding Entries to a Mutable Dictionary

- setObject:forKey:

Adds a given key-value pair to the dictionary.

NSMutableDictionary *dict =  [NSMutableDictionary dictionary];
[dict setObject:@"Easy" forKey:@"Key1"];
NSLog(@"%@",dict);

OUTPUT

{
    Key1 = Eezy;
}

- setObject:forKeyedSubscript:

Adds a given key-value pair to the dictionary.

NSMutableDictionary *dict =  [NSMutableDictionary dictionary];
[dict setObject:@"Easy" forKeyedSubscript:@"Key1"];
NSLog(@"%@",dict);  

OUTPUT { Key1 = Easy; }

Removing Entries From a Mutable Dictionary

- removeObjectForKey:

Removes a given key and its associated value from the dictionary.

NSMutableDictionary *dict =  [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Easy",@"key2": @"Tutorials"}];
[dict removeObjectForKey:@"key1"];
NSLog(@"%@",dict);

OUTPUT

{
    key2 = Tutorials;
} 

- removeAllObjects

Empties the dictionary of its entries.

NSMutableDictionary *dict =  [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Eezy",@"key2": @"Tutorials"}];
[dict removeAllObjects];
NSLog(@"%@",dict);

OUTPUT

{
}

- removeObjectsForKeys:

Removes from the dictionary entries specified by elements in a given array.

NSMutableDictionary *dict =  [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Easy",@"key2": @"Tutorials"}];
[dict removeObjectsForKeys:@[@"key1"]];
NSLog(@"%@",dict);

OUTPUT

{
    key2 = Tutorials;
}

Parameters

objects	keys
An array containing the values for the new dictionary.	CellAn array containing the keys for the new dictionary. Each key is copied and the copy is added to the dictionary.