【iOS 1 行代码系列】之 一行代码告别复杂视图的 deleg

1. 前言

开发中，自定义视图比较复杂，处理事件比较多的时候
需要使用 delegate 或者 block 来回传事件
层级比较多的时候，嵌套也随之增多
结果就是 delegate 嵌套 delegate 或者 block 嵌套 block
一层一层往上传
写着心累，看着心烦
以后要修改或者维护的时候
跳这里，跳那里，跳半天才找到地方

---

2.正题 - UIResponder

先来一张图：UIResponder及其子类

UIResponder及其子类

UIResponder 有一个属性：nextResponder，下一个响应者
利用这个来回传事件

新建分类：

/// UIResponder+JHRouter.h
@interface UIResponder (JHRouter)

- (void)jh_routerWithSelector:(NSString *)selector
                       sender:(id)sender
                         info:(NSDictionary *)info;

@end

/// UIResponder+JHRouter.m

#import "UIResponder+JHRouter.h"

@implementation UIResponder (JHRouter)

/*
 if an object respondsToSelector: selector
 [object respondsToSelector:NSSelectorFromString(selector)]
 you should do something.

 invoke [super jh_routerWithSelector:selector sender:sender info:info];
 Let the events continue to pass up
 */
- (void)jh_routerWithSelector:(NSString *)selector
                       sender:(id)sender
                         info:(NSDictionary *)info
{
    [[self nextResponder] jh_routerWithSelector:selector
                                         sender:sender
                                           info:info];
}

@end

selector 作为SEL使用时
可以给 NSObject 添加一个分类
然后直接

if ([self respondsToSelector:NSSelectorFromString(selector)]){
    [self performSelector:NSSelectorFromString(selector) withObjects:info];
}

// 分类：

@interface NSObject (PerformSelector)

- (id)performSelector:(SEL)aSelector withObjects:(NSArray *)objects;

@end

#import "NSObject+PerformSelector.h"

@implementation NSObject (PerformSelector)

- (id)performSelector:(SEL)aSelector withObjects:(NSArray *)objects
{
    //
    NSMethodSignature *signature = [[self class] instanceMethodSignatureForSelector:aSelector];

    //
    if (!signature) {
        NSString *reason = [NSString stringWithFormat:@"oops~ unrecognized selector %@ sent to instance %@ : %lx",NSStringFromSelector(aSelector),[self class],(unsigned long)[self hash]];
        @throw [[NSException alloc] initWithName:@"com.haocold" reason:reason userInfo:nil];
        return nil;
    }

    //
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    invocation.target = self;
    invocation.selector = aSelector;

    // parameters
    // first: _cmd
    // second: target
    NSInteger arguments = signature.numberOfArguments - 2;

    //
    NSInteger count = MIN(arguments, objects.count);
    for (int i = 0; i < count; ++i) {
        id obj = objects[i];
        if ([obj isKindOfClass:[NSNull class]]) {
            obj = nil;
        }
        [invocation setArgument:&obj atIndex:i+2];
    }

    //
    [invocation invoke];

    //
    id result = nil;
    if (signature.methodReturnLength != 0) {
        [invocation getReturnValue:&result];
    }

    return result;
}

@end

selector 也可以作为一个标志，identifier

if ([selector isEqualToString:@"xxx"]) {
    // do something with info.
}

sender 表示触发事件的 view，如果不关注这个，可以传 nil

info 表示要传递的参数，每经过一个 Reaponder 可以加入一些新的参数

view1 添加了 view2 , view2 添加了 view3

view3 内

[self.nextResponder jh_routerWithSelector:@"view3" sender:nil info:nil];

view2 内

- (void)jh_routerWithSelector:(NSString *)selector sender:(id)sender info:(NSDictionary *)info
{
    // 给 info 添加一些新的参数
    NSMutableDictionary *newInfo = [[NSMutableDictionary alloc] initWithDictionary:info];
    [newInfo setObject:@"name" forKey:@"xx"];
    [self.nextResponder jh_routerWithSelector:selector sender:sender info:newInfo];
}

view1 内

- (void)jh_routerWithSelector:(NSString *)selector sender:(id)sender info:(NSDictionary *)info{
    NSLog(@"info:%@",info);
    //info:{
    //  xx = name;
    //}
}

3.注意

当把一个 view 添加到加一个 view 的 window 时，回传事件会被打断！！！