Question

I know that you can declare a C function outside of a class, but is it possible to declare a Objective-C method outside of a class?

Example:

// Works
void printHelloC()
{
    NSLog(@"Hello.");
}

// Error
-(void) printHelloOC
{
    NSLog(@"Hello.");
}

int main (int argc, const char * argv[])
{
    @autoreleasepool {
        printHelloC();
        [self printHelloOC];// 'self' obviously would not work but you get the idea
    }
    return 0;
}

Answer 1

It depends. You can do something similar with method adding at runtime:

#import <objc/runtime.h>

void myCustomMethod(id self, SEL _cmd, id arg1, id arg2)
{
    NSLog(@"This is a test, arg1: %@, arg2: %@", arg1, arg2);
}

int main(int argc, char *argv[])
{
    Class NSObjClass = [NSObject class];

    class_addMethod(NSObjClass, @selector(myNewMethod::), (IMP) myCustomMethod, "v@:@@");

    NSObject myObject = [NSObject new];

    [myObject myNewMethod:@"Hi" :@"There"];

    [myObject release];

    return 0;
}

But that is about it outside of a @class construct, and it really just covers up what happens with a category.