iOS Setters和Getters以及未标记的属性名称 [英] iOS Setters and Getters and Underscored Property Names

问题描述

所以我有一个名为description的NSString属性，定义如下：

So I have a NSString property named description, defined as follows:

@property (strong, nonatomic) NSMutableString *description;

我在定义getter时可以将它称为_description，如下所示：

I'm able to refer to it as _description when I define the getter, as follows:

- (NSString *)description
{
    return _description;
}

但是，当我定义一个setter时，如下所示：

However, when I define a setter, as follows:

-(void)setDescription:(NSMutableString *)description
{
    self.description = description;
}

它从前面提到的getter（未声明的标识符）中断了_description。我知道我可能只是使用self.description，但为什么会这样呢？

It breaks _description from the aforementioned getter (undeclared identifier). I know I can probably just use self.description instead, but why does this happen?

推荐答案

@borrrden的答案非常好。我只是想补充一些细节。

@borrrden 's answer is very good. I just want to add some details.

属性实际上只是语法糖。因此，当您声明属性时：

Properties are actually just syntax sugar. So when you declare a property like you did:

@property (strong, nonatomic) NSMutableString *description;

它是自动合成的。含义：如果你不提供自己的getter + setter（参见borrrden的答案），就会创建一个实例变量（默认情况下它的名称为underscore + propertyName）。 getter + setter根据您提供的属性描述（强大，非原子）合成。
所以当你得到/设置属性时，它实际上等于调用getter或seter。所以

It is automatically synthesized. What it means: if you don't provide your own getter + setter (see borrrden's answer), an instance variable is created (by default it has name "underscore + propertyName"). And getter + setter are synthesized according to the property description that you provide (strong, nonatomic). So when you get/set the property, it is actually equal to calling the getter or the seter. So

self.description;

等于 [自我描述] 。
和

self.description = myMutableString;

等于 [self setDescription：myMutableString];

因此，当你像你一样定义一个setter：

Therefore when you define a setter like you did:

-(void)setDescription:(NSMutableString *)description
{
    self.description = description;
}

它会导致无限循环，因为 self.description = description; 调用 [self setDescription：description]; 。

It causes an infinite loop, since self.description = description; calls [self setDescription:description];.

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