March 2013
Intermediate to advanced
1000 pages
34h 51m
English
Content preview from Programming iOS 6, 3rd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Class Methods
Class methods are useful in general for two main purposes:
- Factory methods
-
A factory method is a method that dispenses an instance of that class. For example, the UIFont class has a class method
fontWithName:size:. You supply a name and a size, and the UIFont class hands you back a UIFont instance corresponding to a font with that name and size. A class method that vends a singleton instance, such as appears at the end of Chapter 1, is also a factory method. - Global utility methods
-
Classes are global (visible from all code, Chapter 13), so a class is a good place to put a utility method that anyone might need to call and that doesn’t require the overhead of an instance. For example, the UIFont class has a class method
familyNames. It returns an array of strings (that is, an NSArray of NSString instances) consisting of the names of the font families installed on this device. Because this method has to do with fonts, the UIFont class is as good a place as any to put it.
Most methods that you write will be instance methods, but now and then you might write a class method. When you do, your purpose will probably be similar to those examples.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.