How to check for Nil

Question

I am currently studying objective-c and the basic c programming language.

I have a questions about a particular line of code:

if (!balance)

Answer 1

If balance is nil then it will be a pointer to 0x0. That address is never used for a valid object.

In C anything within an if that evaluates to zero is considered a negative response, anything that evaluates to non-zero is a positive response.

Pointers evaluate to their address — exactly as if you cast them to an integral type. The ! means "NOT".

So the test is if(address of balance is not zero).