objective c

Inside every Objective-c method there are two hidden variables id self and SEL _cmd

so

- (void)foo:(id)bar;

is really

void foo(id self, SEL _cmd, id bar) { ... }

and when you call

[someObject foo:@"hello world"]

it is actually

foo( someObject, @selector(foo), @"hello world")

If you cmd-click on NSAssert to jump to it's definition you will see that it is a macro that uses the hidden _cmd variable of the method you are calling it from. This means that if you are not inside an Objective-c method (perhaps you are in 'main'), therefore you don't have a _cmd argument, you cannot use NSAssert.

Instead you can use the alternative NSCAssert.