Tiny demo of -respondsToSelector:

responds.m

/* Compile and run with:
$> clang responds.m -ObjC -std=c99 -framework Foundation
$> ./a.out
*/

#import <Foundation/Foundation.h>

@interface Foo : NSObject
- (int)bar;
@end

@implementation Foo
- (int)bar { return 42; }
@end

int main(int argc, char *argv[]) {
	id foo = [Foo new];
	if ([foo respondsToSelector:@selector(bar)]) {
		NSLog(@"foo responds to bar");
	} 
	if ([foo respondsToSelector:@selector(baz)]) {
		NSLog(@"foo responds to baz");
	}
	[foo release];
}