做iOS開發(fā)的都知道UIButton的繼承關(guān)系,如下
UIButton-->UIControl-->UIView-->UIResponder-->NSObject
這個(gè)控件的創(chuàng)建設(shè)置以及用法就不多說了憨琳，下面說說今天的重點(diǎn)椎侠。以UIButton為例姿染，平時(shí)在用UIButton的時(shí)候伐憾，給當(dāng)前button添加事件處理方法就是調(diào)用它的addTarget:<#(nonnull id)#> action:<#(nonnull SEL)#> events:<#(customButtonType)#>勉痴，然后再在方法里完成對(duì)事件的處理。但是這樣寫的話树肃，代碼的閱讀性就降低了很多蒸矛，那怎么寫才能在創(chuàng)建這個(gè)button地方順帶將它的事件處理方法就敲了呢？

UIButton的Category

但是給UIButton添加之后Category之后不可能就只寫我們這一次要做的事件處理啊乡话，怎么辦？畢竟是給button添加方法耳奕，每個(gè)button都有不同的事件處理绑青，這個(gè)時(shí)候Runtime就能幫我們一個(gè)大忙-動(dòng)態(tài)綁定。具體實(shí)現(xiàn)：
.h

//
//  UIButton+block.h
//  RuntimeTest
//
//  Created by Hongfei Zhai on 2017/11/22.
//  Copyright ? 2017年 Hongfei Zhai. All rights reserved.
//

#import <UIKit/UIKit.h>
//使用runtime調(diào)用的庫(kù)
#import <objc/runtime.h>

typedef void(^TouchBlock)(UIButton *sender);

@interface UIButton (block)

- (void)touchWithEvents:(UIControlEvents )controlEvents withBlock:(TouchBlock)touchBlock;

@end

.m

//
//  UIButton+block.m
//  RuntimeTest
//
//  Created by Hongfei Zhai on 2017/11/22.
//  Copyright ? 2017年 Hongfei Zhai. All rights reserved.
//

#import "UIButton+block.h"

static const void *TouchKey = &TouchKey;

@implementation UIButton (block)

- (void)touchWithEvents:(UIControlEvents)controlEvents withBlock:(TouchBlock)touchBlock {
    //通過一個(gè)key綁定block到相對(duì)應(yīng)的button
    objc_setAssociatedObject(self, TouchKey, touchBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
    //在這里添加action
    [self addTarget:self action:@selector(buttonClick:) forControlEvents:(controlEvents)];
}

- (void)buttonClick:(UIButton *)sender {
    // 通過key獲取到對(duì)應(yīng)button的block回調(diào)
    TouchBlock touchblock = objc_getAssociatedObject(sender, TouchKey);
    if (touchblock) {
        touchblock(sender);
    }
}

@end

使用

    UIButton *button = [UIButton buttonWithType:(UIButtonTypeCustom)];
    button.frame = CGRectMake(0, 0, 100, 50);
    button.center = self.view.center;
    button.backgroundColor = [UIColor redColor];
    button.tag = 10001;
    [button touchWithEvents:(UIControlEventTouchUpInside) withBlock:^(UIButton *sender) {
        NSLog(@"sender.tag === %ld",(long)sender.tag);
    }];
    [self.view addSubview:button];

只用UIButton做了一個(gè)例子屋群，通過它的繼承關(guān)系可以看出控件很多都可以添加block來回調(diào)做出事件的處理闸婴。底下用View來做出一個(gè)類似button的功能控件來說明target-action核心機(jī)制：

//
//  Test_Button.h
//  RuntimeTest
//
//  Created by Hongfei Zhai on 2017/11/22.
//  Copyright ? 2017年 Hongfei Zhai. All rights reserved.
//

#import <UIKit/UIKit.h>

typedef enum customButtonType{
    
    customButtonTypeTouchDown,//按下響應(yīng)
    customButtonTypeTouchUpInside//抬起響應(yīng)
    
}customButtonType;


@interface Test_Button : UIView


- (void)addTarget:(nonnull id)target action:(nonnull SEL)action events:(customButtonType)eventsType;


@end

//
//  Test_Button.m
//  RuntimeTest
//
//  Created by Hongfei Zhai on 2017/11/22.
//  Copyright ? 2017年 Hongfei Zhai. All rights reserved.
//

#import "Test_Button.h"

@interface Test_Button ()
{
    id myTarget;//執(zhí)行按鈕回調(diào)方法的對(duì)象
    SEL myAction;//按鈕的回調(diào)方法
}

@property (nonatomic,assign) customButtonType btnType;//觸發(fā)按鈕回調(diào)方法的枚舉值

@end

@implementation Test_Button

//添加點(diǎn)擊事件的方法
- (void)addTarget:(id)target action:(nonnull SEL)action events:(customButtonType)eventsType{
    self.btnType = eventsType;
    myTarget = target;
    myAction = action;
}
//手指觸碰按鈕，調(diào)用此方法
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    //調(diào)用按鈕的type為touchDown的時(shí)候在調(diào)用按鈕的回調(diào)方法芍躏，如果不是邪乍，就不能調(diào)用按鈕的回調(diào)
    if (self.btnType == customButtonTypeTouchDown) {
        //調(diào)用按鈕的回調(diào)方法 目標(biāo)動(dòng)作機(jī)制的核心 object - 回調(diào)方法的參數(shù)
        [myTarget performSelector:myAction withObject:self];
    }
    
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    if (self.btnType == customButtonTypeTouchUpInside) {
        //調(diào)用按鈕的回調(diào)方法 目標(biāo)動(dòng)作機(jī)制的核心 object - 回調(diào)方法的參數(shù)
        [myTarget performSelector:myAction withObject:self];
    }
}
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

}
@end

用過BlocksKit都知道其中給控件添加block回調(diào)的機(jī)制也是通過runtime來實(shí)現(xiàn)的

BlocksKit添加事件處理的實(shí)現(xiàn)

當(dāng)然BlocksKit功能強(qiáng)大的多，邏輯也更加縝密纸肉，原理還是這個(gè)原理溺欧。而Runtime的使用會(huì)有出乎意料的幫助。