前言：代理delegate只能实现“一对一”的通信，也即一般情况下，一个委托方只能有一个代理方，多次设置只是代理的替换，并不能实现多个代理；但有时我们却有需要多个代理的需求，这个时候该怎么办呢？

“多播代理”应用而生，实现机制如下：

方式一：

#import <UIKit/UIKit.h>
@protocol ViewControllerDelegate<NSObject>
- (void)test;
@end
@interface ViewController : UIViewController
/** 添加代理至数组中 */
- (void)addDelegate:(id)delegate;
@end

----------------ViewControllerBridge.h/.m文件-------------------
.m文件中声明了一个小文件：桥文件
#import "ViewController.h"

@interface ViewControllerBridge:NSObject
@property (nonatomic, retain) id<ViewControllerDelegate>delegate;
@end

@implementation ViewControllerBridge
- (void)dealloc{
    NSLog(@"-------dealloc: bridge-------");
}
@end

----------------------ViewController.m 文件----------------------
#import "SecondController.h"
#import "ThirdController.h"
@interface ViewController ()
@property (nonatomic, retain) NSMutableArray *delegates;
@property (nonatomic, retain) SecondController *svc;
@property (nonatomic, retain) ThirdController *tvc;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.svc = [[SecondController alloc]init];
    self.tvc = [[ThirdController alloc]init];
    [self addDelegate:self.svc];
    [self addDelegate:self.tvc];
    
}
-(void)addDelegate:(id)delegate{
    ViewControllerBridge *bridge = [[ViewControllerBridge alloc]init];
    bridge.delegate = delegate;
    [self.delegates addObject:bridge];
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    for (ViewControllerBridge *bridge in self.delegates) {
        if (bridge.delegate && [bridge.delegate respondsToSelector:@selector(test)]) {
            [bridge.delegate test];
        }
    }
}
- (NSMutableArray *)delegates{
    if (!_delegates) {
        _delegates = [NSMutableArray array];
    }
    return _delegates;
}
- (void)dealloc{
    NSLog(@"-------dealloc: ViewController-------");
}
@end

效果图

核心实现方式：
不是delegate的多次设置，而是添加一个中间文件，每次创建一个新对象，并将代理绑定到该对象中，而后再添加至委托的【代理】数组中。发送消息时，遍历该数组，“剥离出”被绑定的代理，而后执行协议方法即可。

思考：为什么将新文件置于主题文件中？？？

当然独立出来也可以实现相同的效果，前者主要是为了更加紧凑而已。

----------------------ViewController.h 文件----------------------
#import <Foundation/Foundation.h>
#import "ViewController.h"
@interface BridgeDelegate : NSObject
@property (nonatomic, weak) id<ViewControllerDelegate>delegate;
@end

----------------------ViewController.m 文件----------------------
#import "BridgeDelegate.h"
@implementation BridgeDelegate
- (void)dealloc{
    NSLog(@"-------dealloc:BridgeDelegate----------");
}
@end

方式二：

业务逻辑

----------------------CHJSecondController.h 文件----------------------
#import <UIKit/UIKit.h>
@protocol CHJSecondControllerDelegate <NSObject>
@optional
- (void)test;
@end
@interface CHJSecondController : UIViewController
@end

----------------------CHJSecondController.m 文件----------------------
#import "CHJSecondController.h"
#import "CHJMultiDelegate.h"
#import "Dog.h"
#import "Cat.h"
#import "Pig.h"
@interface CHJSecondController ()
@property (nonatomic, strong) NSMutableArray *delegates;
@property (nonatomic, retain) CHJMultiDelegate *multiDelegate;
@property (nonatomic, retain) Dog *dog;
@property (nonatomic, retain) Cat *cat;
@property (nonatomic, retain) Pig *pig;
@end
@implementation CHJSecondController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor greenColor];
    self.multiDelegate = [[CHJMultiDelegate alloc]init];
    self.dog = [[Dog alloc]init];
    self.cat = [[Cat alloc]init];
    self.pig = [[Pig alloc]init];
    [self.multiDelegate addDelegate:self.dog];
    [self.multiDelegate addDelegate:self.cat];
    [self.multiDelegate addDelegate:self.pig];
    self.delegates = self.multiDelegate.delegates;
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    for (id delegate in self.delegates) {
        BOOL isTrue = delegate && [delegate respondsToSelector:@selector(test)];
        NSLog(@"result = %d",isTrue);
        if (isTrue) {
            [delegate test];
        }
    }
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    [self dismissViewControllerAnimated:YES completion:nil];
}
- (void)dealloc{
    NSLog(@"dealloc:%@被释放了！",self);
}
@end

----------------------CHJMultiDelegate.h 文件----------------------
#import <Foundation/Foundation.h>
#import "ViewController.h"
@interface CHJMultiDelegate : NSObject
@property (nonatomic, readonly) NSPointerArray *delegates;
- (void)addDelegate:(id)delegate;
- (void)deleteDelegate:(id)delegate;
@end

----------------------CHJMultiDelegate.m 文件----------------------
- (instancetype)init {
    self = [super init];
    if (self) {
        _delegates = [NSPointerArray weakObjectsPointerArray];
    }
    return self;
}
- (void)addDelegate:(id)delegate{
    if (!delegate) return;
    [_delegates addPointer:(__bridge void *)delegate];
}
- (void)deleteDelegate:(id)delegate{
    for (int i = 0; i < _delegates.count; i++) {
        id instance = [_delegates pointerAtIndex:i];
        if (instance == (__bridge void *)delegate) {
            [_delegates removePointerAtIndex:i];
        }
        [_delegates compact];
    }
}