Message forwarding

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    NSMethodSignature * __block signature = nil;
    [self.implementations enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        signature = [obj methodSignatureForSelector:sel];
        *stop = (nil != signature);
    }];
    return signature;
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    BOOL __block result = NO;
    [self.implementations enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        result = [obj respondsToSelector:aSelector];
        *stop = result;
    }];
    return result;
}

- (void)forwardInvocation:(NSInvocation *)invocation {
    BOOL __block result = NO;
    @weakify(invocation)
    [self.implementations enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        @strongify(invocation);
        result = [obj respondsToSelector:invocation.selector];
        if (result) {
            [invocation invokeWithTarget:obj];
            [invocation retainArguments];
        }
        *stop = result;
    }];
    if (!result) {
        [super forwardInvocation:invocation];
    }
}