问题描述
我很难在self和下划线之间访问Objective c中的属性，无论何时我们创建属性，它的getter-setter都会自动生成。因此，我们可以使用self.property访问相同的属性，并且与_property相同。在我看来，应该有一些不同之处，我没有得到。请告诉我一些例子。
I am so confused between self and underscore to access the property in Objective c, whenever we create property, its getter-setter automatically generated. So we can access the same property with self.property and same as _property. In my opinion, there shoulb be some difference which i am not getting. PLease tell me with examples.
推荐答案
下划线（下划线）版本是实际的实例变量，不应直接引用。你应该总是通过属性名称，这将确保任何getter / setter操作都得到尊重。
The underbar (underscore) version is the actual instance variable, and should not be referenced directly. You should always go via the property name, which will ensure that any getter/setter actions are honoured.
所以如果你做 _property = 4 ，您已直接设置变量。如果你执行 self.property = 4 ，你实际上正在调用方法 [self setProperty：4] ，将通过setter（可能会执行诸如强制执行属性最大值为3的操作，或更新UI以反映新值）。
So if you do _property = 4, you have directly set the variable. If you do self.property = 4, you are effectually making the method call [self setProperty:4], which will go via the setter (which might do something such as enforce property having a max value of 3, or updating the UI to reflect the new value, for example).
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