为什么Xcode 4自动生成实例变量？ [英] Why does Xcode 4 auto-generate a instance variable?

问题描述

我来自C＃开发，刚开始学习Objective-C和Xcode 4.
据我所知，@synthesize正在替换属性的getter / setter方法，如果你不需要检查/控制正在读取或写入的值。

I'm coming from C# development and just started to learn Objective-C and Xcode 4. As far as I understand "@synthesize" is replacing getter/setter methods for properties if you don't need to check/control the values which are being read or written.

但为什么Xcode 4会自动为我创建一个实例变量？

But why does Xcode 4 create a instance variable for me automatically?

这还不够：

@synthesize myProperty;

而不是：

@synthesize myProperty = _myProperty;

？

我为什么要这样做？如果我没有/需要任何getter或setter，请使用/拥有实例变量而不是实际属性？

Why would I want to use/have the instance variable instead of the actual property if I don't have/need any getters or setters?

提前致谢！

MemphiZ

编辑：

我明白了@synthesize正在取代getters / setter但这部分的优点是什么： = _myProperty; ？
如果我可以直接使用myProperty，为什么我想要一个实例变量？如果例如setter检查值的条件，我会理解使用_myProperty。如果我想跳过这个检查，我会使用_myProperty。但是当我使用@synthesize时，我没有一个可以进行检查的setter。那么我为什么要/想要一个实例变量呢？

I understand that @synthesize is replacing getters/setters but what is this part good for: = _myProperty;? Why would I want to have a instance variable if I could use "myProperty" directly? I would understand using "_myProperty" if the setter for example would check for a condition of the value. If I then want to skip this check I would use _myProperty. But as I use @synthesize I don't have a setter in place that does some check. So why do I have/want an instance variable then?

答案：

请参阅MattyG帖子中的评论！

See the comments in MattyG's post!

推荐答案

这是一个用于提醒程序员通过setter访问实例变量的约定和自己的吸气剂。所以，如果你正在使用：

This is a convention used to remind the programmer to access the instance variables through the setters and getters with self. So if you're using:

@synthesize myProperty = _myProperty;

然后直接访问变量你必须写：

Then to access the variable directly you must write:

_myProperty = something;

要通过它的setter访问变量，你必须写：

To access the variable through it's setter you must write:

self.myProperty = something;

如果您忘记通过自己访问，则可获益。那么编译器会警告你：

The benefit is that if you forget to access through self. then the compiler will warn you:

myProperty = something;  //this won't compile

这也是问题。

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