How do I test if a primitive in Objective-C is nil?

Question

I'm doing a check in an iPhone application -

int var;
if (var != nil)

It works, but in X-Code this is generating a warning "comparison between pointer and integer." How do I fix it?

I come from the Java world, where I'm pretty sure the above statement would fail on compliation.

Answer 1

Primitives can't be nil. nil is reserved for pointers to Objective-C objects. nil is technically a pointer type, and mixing pointers and integers will without a cast will almost always result in a compiler warning, with one exception: it's perfectly ok to implicitly convert the integer 0 to a pointer without a cast.

If you want to distinguish between 0 and "no value", use the NSNumber class:

NSNumber *num = [NSNumber numberWithInt:0];
if(num == nil)  // compare against nil
    ;  // do one thing
else if([num intValue] == 0)  // compare against 0
    ;  // do another thing