Objective-c 多播委托 [英] Objective-c multicasting delegates

问题描述

我在 xcode 中创建了新的选项卡式视图项目，在 appdelegate 中我创建了一个协议

I create new tabbed view project in xcode, in appdelegate I created a protocol

.h 文件

@protocol myProtocol <NSObject>
-(void)myProtocolMethodOne;
@end
.
.
.
@property (weak) id<myProtocol> mypDelegate;

.m 文件

@synthesize mypDelegate;
.
.
.
//Inside didFinishLaunchingWithOptions
[mypDelegate myProtocolMethodOne];

在 firstViewController &secondViewController(两者都显示为两个不同的选项卡)我在两者中都这样做了

In firstViewController & secondViewController (both are displayed as two different tab) I did this in both

AppDelegate *ad = (AppDelegate*)[[UIApplication sharedApplication]delegate];
    [ad setMypDelegate:self];
.
.
.
-(void)myProtocolMethodOne
{
    NSLog(@"1st VC");
    [[self tabBarItem]setBadgeValue:@"ok"];
}

代码运行良好，但只有 secondViewController 有响应.

The code is working perfectly but only secondViewController is responding.

我正在寻找一种使用委托而不是通知的广播和侦听器机制.

I am looking for a broadcasting and listener kind of mechanism using delegates not notifications.

我搜索了很多，但确实找到了除this之外的任何解决方案，但代码已提前我理解，所以我通过从一个简单的项目开始，一步一步地理解这一点.请帮我解决这个问题.两个viewcontroller如何同时响应delegate，我该怎么办?

I searched a lot but did find any solutions except this but code is advance for me to understand, so I am taking a step by step approach to understand this by starting form a simple project. Please help me regarding this. How both viewcontrollers can respond to delegate at same time, what should I do?

推荐答案

在您的情况下，通过持有委托数组(可能作为私有属性)并允许添加/删除委托，足以容纳包含所有委托的数组:

In your case is enough to hold an array with all delegates, by holding an array of delegates, possibly as a private property, and allowing to add/remove delegates:

@interface AppDelegate() // .h file

@property (nonatomic,strong,readwrite) NSMutableArray* delegates;

@end 

// .m file

- (void) addDelegate: (id<MyProtocol>) delegate // By convention the first letter should be capital.
{
    // Optional code you may need to execute before adding it.
    [delegates addObject: delegate];
}

我将 removeDelegate 方法留给您，它的实现非常简单.

I leave to you the removeDelegate method, it's very simple to implement.

如何调用委托方法

在每个对象上调用选择器就足够了:

It's enough to call the selector on every object:

[delegates makeObjectsPerformSelector: myProtocolMethodOne];

如果您需要获取返回值，最好这样做:

If you need to take return values it's better to do it this way:

NSMutableArray* returnValues= [NSMutableArray new];
for(id<MyProtocol> delegate in delegates)
{
    id result= [delegate myProtocolMethodTwo]; // Method returning a value
    [returnValues addObject: result];
} 

如何添加代表

在每个控制器中(最多 N 次)，您应该能够添加它:

In every controller (up to N times) you should be able to add it:

AppDelegate *ad = (AppDelegate*)[[UIApplication sharedApplication]delegate];
[ad addDelegate:self];

附加问题:您可能想要弱委托，但 NSArray 拥有强引用.在这里你可以找到一个很好的解决方案:

Additional problem: You may want to have weak delegates, but a NSArray holds strong references. Here you can find a nice solution for this:

ARC 下对象的弱引用 (__unsafe_unretained) 数组

它基本上是说使用 NSValue 使用 valueWithNonretainedObject 方法来存储弱引用.

It basically says to use NSValue to store weak reference using the valueWithNonretainedObject method.

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