How to Use Objective-C Dictionaries

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How to Use Dictionaries

Like an array, a dictionary is a list of objects. However, dictionaries make it
easier to organize data by providing “keys” that make it a snap to find the
things you put in there. These are sometimes referred to as a hash or a
hash-table.

Instantiate a dictionary

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

Add objects to a dictionary indexed by keys

[dictionary setObject:@"A Book about the Letter A" forKey:@"A"];
[dictionary setObject:@"A Book about the Letter B" forKey:@"B"];
[dictionary setObject:@"A Book about the Letter C" forKey:@"C"];

Retrieve an object from a dictionary with a key

NSLog([dictionary objectForKey:@"B"]);

Release a dictionary

[dictionary release]; 

Cool – hope you enjoyed this snippet of da codes! Once you get use to the square brackets and verbose parameter prefixes Objective-C starts to feel like the programming languages that you are used to.