StackOverflow2013

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copied!<p>The <a href="http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSDictionary_Class/Reference/Reference.html" rel="noreferrer">NSDictionary</a> and <a href="http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSMutableDictionary_Class/Reference/Reference.html#//apple_ref/occ/cl/NSMutableDictionary" rel="noreferrer">NSMutableDictionary</a> docs are probably your best bet. They even have some great examples on how to do various things, like...</p> <p><strong>...create an NSDictionary</strong></p> <pre><code>NSArray *keys = [NSArray arrayWithObjects:@"key1", @"key2", nil]; NSArray *objects = [NSArray arrayWithObjects:@"value1", @"value2", nil]; NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys];</code></pre> <p><strong>...iterate over it</strong></p> <pre><code>for (id key in dictionary) { NSLog(@"key: %@, value: %@", key, [dictionary objectForKey:key]); }</code></pre> <p><strong>...make it mutable</strong></p> <pre><code>NSMutableDictionary *mutableDict = [dictionary mutableCopy];</code></pre> <p><em>Note: historic version before 2010: [[dictionary mutableCopy] autorelease]</em></p> <p><strong>...and alter it</strong></p> <pre><code>[mutableDict setObject:@"value3" forKey:@"key3"];</code></pre> <p><strong>...then store it to a file</strong></p> <pre><code>[mutableDict writeToFile:@"path/to/file" atomically:YES];</code></pre> <p><strong>...and read it back again</strong></p> <pre><code>NSMutableDictionary *anotherDict = [NSMutableDictionary dictionaryWithContentsOfFile:@"path/to/file"];</code></pre> <p><strong>...read a value</strong></p> <pre><code>NSString *x = [anotherDict objectForKey:@"key1"]; </code></pre> <p><strong>...check if a key exists</strong></p> <pre><code>if ( [anotherDict objectForKey:@"key999"] == nil ) NSLog(@"that key is not there"); </code></pre> <p><strong>...use scary futuristic syntax</strong></p> <p><em>From 2014 you can actually just type dict[@"key"] rather than [dict objectForKey:@"key"]</em></p>

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