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Don't use accessor methods in init and dealloc

 2 years ago
source link: https://fann.im/blog/2012/08/14/dont-use-accessor-methods-in-init-and-dealloc/
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Don't use accessor methods in init and dealloc

Aug 14, 2012

苹果在 WWDC 2012 Session 413 - Migrating to Modern Objective-C 里强调不要在 init 和 dealloc 里使用 accessor methods：

Always use accessor methods. Except in initializer methods and dealloc.

之前没有注意过这种情况，稍微搜索学习了一下。文档 Memory Management 里确实有这说法：

The only places you shouldn’t use accessor methods to set an instance variable are in initializer methods and dealloc.

提倡下面这种写法：

- (id)init {
    self = [super init];
    if (self) {
        _count = [[NSNumber alloc] initWithInteger:0];
    }
    return self;
}

- (id)initWithCount:(NSNumber *)startingCount {
    self = [super init];
    if (self) {
        _count = [startingCount copy];
    }
    return self;
}

dealloc 不能用比较好理解，self.property 是向 property 发了一个消息，有可能该对象的生命周期已经结束，不能再接受消息。init 不能用比较靠谱的说法是如果有 subClass 并重载了 accessor，那么 init 里 self.property 就无效；另外也可能会有其他影响，比如 KVC notifications 等。

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