I usually prefer the more explicit form (of any expression) because it more
obviously describes what is happening. That is your second example. However,
anyone who works with any variant of C quickly becomes comfortable with the
first form, so I consider it quite acceptable.
There is another form you will see,
if (self = [super init]) .....
It compacts the assignment into the boolean. It works, but putting an
assignment into a boolean is treading close to the edge of being misleading.
Too clever by half, as the British say.
David
On Feb 24, 2012, at 6:50 AM, Oleg Krupnov wrote:
> An interesting question. The following samples are equivalent in terms
> of compiled code, but which one is more correct from the language's
> point of view?
>
> self = [super init];
> if (self)
> {
> }
> return self;
>
> self = [super init];
> if (self != nil)
> {
> }
> return self;
>
> The Xcode samples promote the first variant, but I'm wondering if the
> second one is more correct?
>
> The "nil" is defined as follows (jumped to definition)
>
> #define nil NULL
> #define NULL ((void*)0)
>
> So basically, nil is of type "void*", so the expression "self != nil"
> compares two pointers and the result is "boolean", which is perfect
> for testing in the "if" statement. But the "self" alone is of type
> "pointer" and so when it is tested by the "if" statement, it's
> implicitly cast to the type "boolean".
>
> I also heard that generally speaking NULL is not necessarily always
> equal to 0 on all architectures.
>
> Thoughts?
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