Objective-C：_variable [英] Objective-C: _variable

问题描述

好的，这个问题以前一定是问过的，但我看起来很生气，没有发现任何东西：

我的iphone应用程序中有一个简单的数组，我定义如下：

  @property（nonatomic，strong）NSArray * pages; 
 @synthesize pages = _pages; 
  

我在Apples示例代码中看到了这个，认为这是编写自我的好捷径.pages（即_pages替换self.pages）就像这样：

  _pages = [[NSArray alloc] init]; 
  

但是Apple又有这个功能（并不完全像这样，但是看起来好像它们会随机交换）：

  self.pages = [NSKeyedUnarchiver unarchiveObjectWithData：contents]; 
  

最后：

  [_ pages release]; 
  

这完全让我感到困惑。 _pages和self.pages之间有什么区别？

感谢您的帮助。

解决方案

_pages 是对象的 ivar 的名称。 页面是不同的属性名称。

因此， @synthesize pages = _pages; 最后告诉页面是ivar _pages 的属性。

您将通过 _pages 在初始化程序和dealloc方法中嵌入ivar直接访问。其他地方，属性名称用于获取/设置其值。

OK, this must have been asked before but I looked like mad and found nothing:

I have a simple array in my iphone app which I define like so:

@property (nonatomic, strong) NSArray *pages;
@synthesize pages = _pages;

I've seen this in Apples sample code and thought this is a nice short-cut for writing self.pages (i.e. _pages replaces self.pages) like so:

_pages = [[NSArray alloc] init];

but then Apple has this again (not exactly like this, but it appears as if they keep swapping randomly):

self.pages = [NSKeyedUnarchiver unarchiveObjectWithData:contents];

And finally:

[_pages release];

Which totally confuses me. What would be the difference between _pages and self.pages?

Thanks for your help.

解决方案

_pages is the name of the object's ivar. pages is the property name which is different.
So, @synthesize pages = _pages; finally tells that pages is the property for the ivar _pages.

You will encouter the ivar direct access via _pages in initializers and dealloc methods. Every where else, the property name is used to get/set its value.

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