gistfile1.m

@protocol NamedObject <NSObject>
-(NSString*)name;
@end

/////////////////

@interface User : NSObject
-(NSString*)name;
@end

/////////////////

@interface Greeter : NSObject
@end

@implementation Greeter
-(id)init {
	if (self=[super init]) {
		User* user=[[User alloc] init];
		[self sayHi:user];  // Sending 'User *__strong' to parameter of incompatible type 'id<NamedObject>'
	}
	return self;
}
-(void)sayHi:(id<NamedObject>)object {
	NSLog(@"Hi %@", object.name);
}
@end