iPhone - 当[super init]失败时使用self = [super init] [英] iPhone - Use of self = [super init] when [super init] fails

问题描述

有什么区别：

// 1
-(id) init {
    self = [super init];
    if (self) {
        ... do init ....
    }
    return self;
}

// 2 - I guess it's exactly the same as previous
-(id) init {
    if (self = [super init]) {
        ... do init ....
    }
    return self;
}

// 3 - is this one a really bad idea and if yes, Why ?
-(id) init {
    self = [super init];
    if (!self) return nil;

    ... do init ....

    return self;
}

// 4 - I think this one sounds OK, no ? But what is returned... nil ?
-(id) init {
    self = [super init];
    if (!self) return self;

    ... do init ....

    return self;
}

编辑：感谢Peter M。

EDIT : Added thanks to Peter M.

// 5 - I really like the readability of this one
-(id) init {
    if(!(self = [super init])) return self;  // or nil

    ... do init ....

    return self;
}

推荐答案

1. Apple使用的常用文件


2. 是否相同，但编译器不知道你是不是指 == 而不是 = 。您可以通过在表达式周围使用另一个（...）来阻止警告，但这并不容易阅读。


3. 这个任何好的编码标准都会优先考虑（通常不是单线，而是带有护腕）。当您的初始化代码很长时，这会显着提高可读性。


4. 与3相同，但您失去了一些可读性。返回 nil 使代码更容易理解（也许这只是我的意见，其他人可以说4优于3）。

1. The common one used by Apple
2. Does the same but the compiler does not know if you didn't mean == instead of =. You can block the warning by using another (...) around the expression, but it's not easy to read.
3. This one would be preferred by any good coding standards (usually not as a one-liner but with bracers). When your initialization code is long, this one significantly increase readibility.
4. The same as 3 but you lose some readibility. Returning nil makes the code easier to understand (maybe this is only my opinion, someone else can say 4 is better than 3).

总结：使用1或3.当初始化代码很长时，你应该使用3来避免大多数方法代码在一个中，如果阻止。 Apple仅使用1但不盲目跟随它。 Apple没有记录编码标准，有时他们推荐的内容非常值得怀疑。

In summary: use 1 or 3. When initialization code is long, you should use 3 to avoid having most of method code in one if block. Apple uses only 1 but don't follow it blindly. Apple has no documented coding standards and sometimes what they recommend is very questionable.

你可以用4而不是3但不要混用3&你的代码中有4个。

You can use 4 instead of 3 but don't mix 3 & 4 in your code.

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