[Obj-C] if (self) vs. if (self != nil)
[Obj-C] if (self) vs. if (self != nil)
- Subject: [Obj-C] if (self) vs. if (self != nil)
- From: Oleg Krupnov <email@hidden>
- Date: Fri, 24 Feb 2012 16:50:06 +0200
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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