Question

Possible Duplicate:
ObjectiveC: if (obj) {…} AND if (obj != nil) {…}, which is better?

Is there a difference between these two conditions:

if (!object) {
 // do something
}

and . . .

if (object == nil) {
 // do something
}

Answer 1

No, there is no difference. Both of those examples are exactly the same. From the C spec 6.5.3.3 Unary arithmetic operators:

The result of the logical negation operator ! is 0 if the value of its operand compares unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int. The expression !E is equivalent to (0==E).

Since nil is 0, that last sentence applies exactly.