属性名称的下划线前缀？ [英] Underscore prefix on property name?

问题描述

可能重复：

Possible Duplicate:
How does an underscore in front of a variable in a cocoa objective-c class work?

任何人都可以指示使用下划线的说明，我一直假设他们用于强调您正在访问iVar [_ window release]; ，而不是通过setter / getter方法访问iVar [[self window] release ]; 或 [self.window release]; 我只想验证我的理解是否正确。

Can anyone point me to an explanation of the use of underscores, I have always assumed that they are used to highlight that you are accessing the iVar [_window release]; rather than accessing the iVar via a setter/getter method [[self window] release]; or [self.window release]; I just want to verify that my understanding is correct.

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UILabel *markerLabel;

@synthesize window = _window;
@synthesize markerLabel = _markerLabel;

推荐答案

对于ivar名称使用下划线是一个约定首先被苹果用于区分实际ivar和财产。

The use of an underscore for ivar names is a convention first used by Apple to differentiate between an actual ivar and a property. Many people have since adopted this convention.

这样做的原因是为了防止向ivar而不是给实际的setter分配一个新值的错误：

The reason this is done is to prevent the mistake of assigning a new value to an ivar instead of to the actual setter:

myIvar = newValue;

而不是

self.myIvar = myValue;

如果您不小心使用了顶层示例，则可能导致内存泄漏。下划线可防止您犯这个错误。

If you accidentally use the top example, you could cause a memory leak. The underscore prevents you from making that mistake.

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