MsgForward

- (void)helloWorld
{
    NSLog(@"hello world");
}

// 使用 resolveInstanceMethod: 动态方法解析的前提是：动态新增的方法必须已经实现过了
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    if (sel == @selector(printFirstAdd))
    {
        IMP methodAddress = [self instanceMethodForSelector:@selector(helloWorld)];
        class_addMethod(self, sel, methodAddress, "v@:");    
        return YES;
    }
    return NO;
}

@implementation SecondFind

+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    return NO;
}

// 寻找备援接收者
- (id)forwardingTargetForSelector:(SEL)aSelector
{
    if (aSelector == @selector(printSecondFind))
    {
        return [OtherClass new];
    }
    return [super forwardingTargetForSelector:aSelector];
}

@end


@implementation OtherClass

- (void)printSecondFind
{
    NSLog(@"我是备援接收者，我可以处理 printSecondFind 方法");
}

@end

@implementation ThirdInvocation

+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    return NO;
}

- (id)forwardingTargetForSelector:(SEL)aSelector
{
    return [super forwardingTargetForSelector:aSelector];
}

// 启动完整的消息转发，将消息有关的全部细节封装到 NSInvocation 对象中

// 1. 必须重写 methodSignatureForSelector: 方法，才会执行 forwardInvocation: 方法
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
    // 返回方法签名
    if (aSelector == @selector(printThirdInvocation))
    {
        return [NSMethodSignature signatureWithObjCTypes:"v@:"];
    }
    return [super methodSignatureForSelector:aSelector];
}


// 2. 启动完整的消息转发
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    // 方式 1. 可通过改变 target 方法调用者 来完成消息转发
    // [anInvocation invokeWithTarget:[OtherObject new]];
    
    // 方式 2. 可通过改变 selector 选择子 来完成消息转发
     anInvocation.selector = @selector(printWangRui);
     [anInvocation invoke];
    
    // 方式 3. 可通过改变 参数个数 来完成消息转发
    // 暂没解决
//    NSMethodSignature *signature = [NSMethodSignature signatureWithObjCTypes:"v@:"];
//    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
//    invocation.selector = @selector(printThirdInvocation);
//    NSString *parameter0 = @"我是参数0";
//    NSString *parameter1 = @"我是参数1";
//
//    [invocation setArgument:¶meter0 atIndex:2];
//    [invocation setArgument:¶meter1 atIndex:3];
//    NSLog(@"----- %@",NSStringFromSelector(invocation.selector));
//    [invocation invokeWithTarget:self];
}


- (void)printWangRui
{
    NSLog(@"启动完整的消息转发：可通过改变 selector 选择子 来完成消息转发");
}

- (void)printThirdInvocation:(id)parameter0
{
    NSLog(@"启动完整的消息转发：可通过改变 参数个数 来完成消息转发");
}

- (void)printThirdInvocation:(id)parameter0 :(id)parameter1
{
    NSLog(@"启动完整的消息转发：可通过改变 参数个数 来完成消息转发");
}

@end


@implementation OtherObject

- (void)printThirdInvocation
{
    NSLog(@"启动完整的消息转发：可通过改变 target 方法调用者 来完成消息转发");
}

@end