在 Obj-C 中使用访问器——这只是语义吗？

发布于 2024-12-14 16:47:23 字数 623 浏览 3 评论 0原文

可能的重复：
我应该使用属性还是直接引用内部访问实例变量？

我一直想知道：是否有任何特殊原因总是使用或不使用访问器方法（方括号或点符号）？每当我合成属性时，我都会这样做...

@synthesize aProperty = _aProperty;

然后在我的代码中，我总是使用 self.aProperty 而不是 _aProperty。

在我看来，始终使用访问器似乎是合乎逻辑的。然而，在大多数示例/教程代码中，作者似乎与这种用法有些不一致，有时 self.aProperty，有时 _aProperty，有时甚至只是 aProperty< /code> （没有在合成中设置别名）。谁能解释为什么建议或不建议始终使用访问器，或者在什么情况下不建议使用？

原文

Possible Duplicate:
Should I use properties or direct reference when accessing instance variables internally?

I have always wondered: is there any particular reason always to use or not use accessor methods (either square brackets or dot notation)? Whenever I synthesize properties, I do so like this...

@synthesize aProperty = _aProperty;

And then throughout my code I always use self.aProperty instead of _aProperty.

It seems to me logical to always use the accessors. However, in most sample/tutorial code, authors seem to be somewhat inconsistent with this usage, sometimes self.aProperty, sometimes _aProperty, and sometimes even just aProperty (without having set the alias in synthesize). Can anyone explain why it would or would not be advisable to always use the accessors, or in which cases would it be not advisable?

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深空失忆 2024-12-21 16:47:30

正如我一直听到的那样，底线是：您应该始终使用合成的 getter 和 setter。但是，有时您需要直接访问变量，特别是当您可能覆盖合成的 getter 或 setter 以返回/设置一些处理后的数据，但还需要从类内部访问原始数据时。

示例：

@synthesize firstName = _firstName;

假设在此示例中您想使用默认设置器，但您想覆盖 getter 以始终返回名字的规范化版本（抱歉，我知道这很奇怪，但我可以在我的顶部想到一个更好的示例）头）。所以你可以做这样的事情。

- (NSString*)getFirstName {
    return [_firstName lowercaseString];
}

每当您使用 [self firstName] 或 self.firstName 时，您都将通过 getter 访问该变量并返回小写版本。但是，如果您仍然需要访问原始变量，您可以使用 _firstName 直接访问它。

Bottom line as I've always heard it: you should always use the synthesized getter and setter. However, there are times when you need to access the variable directly, especially when you may override the synthesized getter or setter to return/set some processed data but need to also access the raw data from inside the class.

Example:

@synthesize firstName = _firstName;

Say in this example you wanted to use the default setter but you wanted to override the getter to always return a normalized version of the first name (sorry, I know its weird but I can think of a better example off the top of my head). So you can do something like this.

- (NSString*)getFirstName {
    return [_firstName lowercaseString];
}

Anytime that you use [self firstName] or self.firstName you will access the variable through the getter and get back a lowercase version. However, if you needed to still access the raw variable you could use _firstName to directly access it.

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