Ios5 programming @ synthesize window = _ window

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@ Synthesize window = _ window;
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@ Synthesize viewController = _ viewController;
Generally, no = part is included. @ synthesize window = _ window. How can this problem be solved? What are the variables of _ window and _ viewController?

In the. h file, no window and viewController instance variables are defined in the class. How can I declare @ perproty?

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# Import <UIKit/UIKit. h> <a href = "http://my.oschina.net/liwenlong7758" target = "_ blank" rel = "nofollow"> @ class </a> ViewController; <a href = "http://my.oschina.net/interface" target = "_ blank" rel = "nofollow"> @ interface </a> AppDelegate: NSObject <UIApplicationDelegate>
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@ Property (nonatomic, retain) IBOutlet UIWindow * window;
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@ Property (nonatomic, retain) IBOutlet ViewController * viewController;
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<A href = "http://my.oschina.net/u/567204" target = "_ blank" rel = "nofollow"> @ end </a>
In 32-bit mode, if the @ interface part of the class is not declared as ivar, but there is a @ property declaration, @ synthesize is returned in the @ implementation part of the class, the following compilation error is returned:
Synthesized property 'xx' must either be named the same as a compatible ivar or must explicitly name an ivar
In 64-bit mode, the system automatically adds ivar to the class during runtime. The added ivar is prefixed with an underscore.
@ Synthesize window = _ window in the Declaration above indicates that the window attribute is the _ window instance variable synthesis accessors method.

Author: it_machine _