talk is cheap

```objc
@protocol YouShouldDoThisDelegate <NSObject>

@optional

- (void )killBill;

@end;
```

```objc
@implementation AClass
{
id<YouShouldDoThisDelegate> _delegate;
}

- (void )findSomeToKillTarget
{
BClass *b = [BClass alloc] init];
_delegate = b;
}

- (void )killOrder
{
if ([_delegate respondsToSelector:@selector (killBill )]) {
[_delegate killBill];
}
}

@end
```

```objc
@interface BClass () <> <YouShouldDoThisDelegate>

@end

@implementation BClass

- (void )killBill
{
//Kill Bill
}

@end
```