Why does not this NSAssert with stringWithFormat compile?

Question

stringWithFormat should return a string, why does this statement not compile

NSAssert(YES, [NSString stringWithFormat:@"%@",@"test if compiles"]);

when

NSAssert(YES, @"test if compiles");

compiles?

Answer 1

Use this as :

NSAssert(YES, ([NSString stringWithFormat:@"%@",@"test if compiles"])); // Pass it in brackets ()

Hope it helps you.

Answer 2

You don't actually need to use stringWithFormat at all. NSAssert already expects you to pass a format string and variable arguments for formatting. Given your example, you'll find this works just as well:

NSAssert(YES, "%@", @"test if compiles");

Or, a more realistic example:

NSAssert(i > 0, @"i was negative: %d", i); 

The reason for your problem is because NSAssert is a macro, defined like this:

#define NSAssert(condition, desc, ...)

And the compiler is confused because there's ambiguity between the parameter list for stringWithFormat and that of the macro itself. As Nishant points out, you can add brackets to avoid the confusion if you really want to use stringWithFormat here.