Uploaded September 2012 | Updated September 2026, 2 weeks ago
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The NSDictionary class declares the programmatic interface to objects that manage immutable associations of keys and values. Use this class or its subclass NSMutableDictionary when you need a convenient and efficient way to retrieve data associated with an arbitrary key. NSDictionary creates static dictionaries, and NSMutableDictionary creates dynamic dictionaries. (For convenience, we use the term dictionary to refer to any instance of one of these classes without specifying its exact class membership.)
A key-value pair within a dictionary is called an entry. Each entry consists of one object that represents the key and a second object that is that key's value. Within a dictionary, the keys are unique. That is, no two keys in a single dictionary are equal. In general, a key can be any object, but note that when using key-value coding the key must be a string.
Subscribe to our channel here for notifications on new video trainings. For more videos on technology, visit our website at http://www.techytube.com.
By pavel@techytube, for more from this author visit:
techytube.com/author/pavel
The NSDictionary class declares the programmatic interface to objects that manage immutable associations of keys and values. Use this class or its subclass NSMutableDictionary when you need a convenient and efficient way to retrieve data associated with an arbitrary key. NSDictionary creates static dictionaries, and NSMutableDictionary creates dynamic dictionaries. (For convenience, we use the term dictionary to refer to any instance of one of these classes without specifying its exact class membership.)
A key-value pair within a dictionary is called an entry. Each entry consists of one object that represents the key and a second object that is that key's value. Within a dictionary, the keys are unique. That is, no two keys in a single dictionary are equal. In general, a key can be any object, but note that when using key-value coding the key must be a string.





![How to customize the NavBar in iOS
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The NavBar or the navigation bar is the top side view that appears by default over our main view if we have a navigation controller presenting the corresponding view controller.
Its dimensions for iPhone and iPod touch are 320 x 44, so if we want to set custom background images for that, we need 2 images: one normal of 320 x 44 pixels, and the other one for Retina Display, of 640 x 88 pixels.
iOS provides us 4 default options for customising the NavBar, and we do that by writing the following line of code:
self.navigationController.navigationBar.barStyle = UIBarStyleDefault;
The barStyle property can be set to one of 4 values, which are:
UIBarStyleDefault,
UIBarStyleBlack,
UIBarStyleBlackOpaque,
UIBarStyleBlackTranslucent.
Starting with iOS 5, it is very easy to set a background image for the NavBar in this way:
UIImage *navBarImage = [UIImage imageNamed:@nav-bar-image];
[[UINavigationBar appearance] setBackgroundImage:navBarImage forBarMetrics:UIBarMetricsDefault]; How to customize the NavBar in iOS](https://i.ytimg.com/vi/kjQ4qVGHr9w/mqdefault.jpg)




