#pragma 是什么

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摘自：《Beginning.iOS.5.Development.Exploring.the.iOS.SDK》

#pragma mark -
#pragma mark Picker Data Source Methods
Any line of code that begins with #pragma is technically a compiler directive. More specifically, a #pragma marks a pragmatic, or compiler-specific, directive that won’t necessarily work with other compilers or in other environments. If the compiler doesn’t recognize the directive, it ignores it, though it may generate a warning. In this case, the  #pragma directives are actually directives to the IDE, not the compiler, and they tell Xcode’s editor to put a break in the popup menu of methods and functions at the top of the editor pane. The first one puts the break in the menu. The second creates a text entry containing whatever the rest of the line holds, which you can use as a sort of descriptive header for groups of methods in your source code.
Some of your classes, especially some of your contro ller classes, are likely to get rather long, and the methods and functions popup menu makes navigating around your code much easier. Putting in #pragma directives and logically organizing your code will make that popup more efficient to use.

 

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