Question

Lately, I saw the following line:

[someObject release], someObject = nil;

Why does this work? Why and under which circumstances can there be several calls separated by , in one row? (Not ;)

Answer 1

Objective C is a superset of C, and , is an operator in C. It evaluates to the last expression in the chain, and creates a sequence point.

Semicolon ; cannot be used in an expression because it is not an operator.

You may have seen the , operator at work in a more common situation that involves for loops:

int i = 0, j = 0;
for ( ; i < 200 ; i++, j += 3) { // This is one of the more typical uses of ','
}