【iOS 1 行代碼系列】之 一行代碼告别複雜視圖的 delegate 和 block

1. 前言

開發中，自定義視圖比較複雜，處理事件比較多的時候

需要使用 ​​

​delegate​

​​ 或者 ​

​block​

​​ 來回傳事件

層級比較多的時候，嵌套也随之增多

結果就是 ​​

​delegate​

​​ 嵌套 ​

​delegate​

​​ 或者 ​

​block​

​​ 嵌套 ​

​block​

​​

一層一層往上傳

寫着心累，看着心煩

以後要修改或者維護的時候

跳這裡，跳那裡，跳半天才找到地方

2.正題 - UIResponder

先來一張圖：UIResponder及其子類

UIResponder 有一個屬性：nextResponder，下一個響應者

利用這個來回傳事件

建立分類：

/// 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​

​​ 作為SEL使用時

可以給 ​​

​NSObject​

​​ 添加一個分類

然後直接

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

// 分類：

@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​

​ 也可以作為一個标志，identifier

if ([selector isEqualToString:@"xxx"]) {
    // do      

​

​sender​

​​ 表示觸發事件的 view，如果不關注這個，可以傳 ​

​nil​

​

​

​info​

​​ 表示要傳遞的參數，每經過一個 ​

​Reaponder​

​ 可以加入一些新的參數

​

​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
{
    // 給 info 添加一些新的參數
    NSMutableDictionary *newInfo = [[NSMutableDictionary alloc] initWithDictionary:info];
    [newInfo setObject:@"name" forKey:@"xx"];
    [self.nextResponder      

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

3.注意