Question

Possible Duplicate:
(Objective-)C ints always initialized to 0?

I have an interface

@interface MyInterface
{
   NSInteger _count;
}

@end

Then in my implementation I am just using is as

if (_count==0)
{
  //do somthing
}
_count++;

And it works i.e. the first time around when this is executed the value is in fact 0 even though I never initialized it to be zero.

Is it because the default value of NSInteger is 0?

Answer 1

Assuming you meant to write == instead of =, the answer is that all of the instance variables (ivars) of an Objective-C class get initialized to 0 or nil when the object gets created. See the question (Objective-)C ints always initialized to 0?.

If you actually wrote if (_count = 0) with a single =, then that’s not doing what you expected — it’s assigning 0 to _count, and then testing if it’s non-zero (the expression if (x) tests if x is non-zero). Since you just assigned 0 to it, it’s not non-zero, so the test will always fail.