Question

我是swift的新手。一些dessign模式的实现让我很困惑。

例如我在java代码中有presudo模式观察者（回调）（下面有例子）。即UI将自己的监听器传递给Manager类，并监听回调isConnected和isDisconnected。如果执行回调，则UI类显示某些消息＆＃34; isConnected＆＃34;或＆＃34; isDisconnected＆＃34;

    public class UI{
        private Manager mManager;
        void createManager(){
            mManager = new Manager(mManagerLister);
        }
        public void showMessage(String aMsg){
            print(aMsg)
        }
        private final IManagerListener mManagerLister = new IManagerListener{
            void isConnected(){
                this.showMessage("isConnected") 
            }
            void isDisconnected(){
                this.showMessage("isConnected")
            }
        }
    }

    public class Manager{
        interface IManagerListener{
            void isConnected();
            void isDisconnected();
        }
        private final mListener; 
        public Manager(IManagerListener aListener){
            mListener = aListener;
        }
    }

如何正确地将此java代码移植到swift代码？我尝试移植但错误消息 类型＆＃39; UI＆＃39;没有会员＆＃39; showMessage＆＃39; 会显示

  public class UI{
    var manager: Manager?
    var managerListener: IManagerListener?
    func createManager(){
        managerListener = ManagerListenerImp(self)  
        manager = Manager(managerListener)
    }
    public func showMessage(msg: String){
        print(msg)
    }
    class ManagerListenerImp: IManagerListener{
        weak var parent: UI 
        init(parent : UI ){
            self.parent = parent
        }
        func isConnected(){
            parent.showMessage("isConnected") 
            // Value of type 'UI' has no member 'showMessage'
            }
        ..........
    } 
}

也许更优雅地存在一种使用回调的方式，我的方式不正确？

Answer 1

有多种方法可以实现它。

委托模式（使用协议，它们只是接口在Java）
使用块/闭包
使用KVO

因为你已经在下面详细说明了委托模式。

修改您的代码，如下所示

声明协议

@objc protocol ManagerListenerImp {
    func isConnected()
}

在Manager类中声明变量

class Manager {
    weak var delegate : ManagerListenerImp? = nil
}

确认您的UI类中的ManagerListenerImp

extension UI : ManagerListenerImp {
    func isConnected () {
        //your isConnected implementation here
    }
}

传递UI实例（swift中的self和JAVA中的这个经理类）

func createManager(){
    manager = Manager()
    manager?.delegate = self
}

最后，每当你想从isConnected课程中触发Manager时，只需说出

self.delegate?.isConnected()

在您的经理类中

希望有所帮助

Answer 2

我对哪个类引用了哪个类有些困惑，但在下面的示例中应该不难改变。

您可能正在寻找观察者模式。这可以让多个对象监听相同的更改：

1。 ManagerStateListener 协议

任何应对管理器状态变化做出反应的类要实现的协议

protocol ManagerStateListener: AnyObject {
    func stateChanged(to state: Manager.State)
}

2.经理类

Manager 类包含：

它的状态
有听众的列表
添加、删除和调用侦听器的方法
实现 ManagerStateListener 协议的示例类


class Manager {
    
    /// The possible states of the Manager
    enum State {
        case one
        case two
        case three
    }
    
    /// The variable that stores the current state of the manager
    private var _currentState: State = .one
    var currentState: State {
        get {
            return _currentState
        }
        set {
            _currentState = newValue
            
            /// Calls the function that will alert all listeners
            /// that the state has changed
            invoke()
        }
    }
    
    /// The list with all listeners
    var listeners: [ManagerStateListener] = []
    
    /// A specific listener that gets initialised here
    let someListener = SomeListener()
    
    init() {
        addListener(someListener) /// Add the listener to the list
    }
    
    /// Method that invokes the stateChanged method on all listeners
    func invoke() {
        for listener in listeners {
            listener.stateChanged(to: currentState)
        }
    }
    
    /// Method for adding a listener to the list of listeners
    func addListener(_ listener: ManagerStateListener) {
        listeners.append(listener)
    }
    
    /// Method for removing a specific listener from the list of listeners
    func removeListener(_ listener: ManagerStateListener) {
        if let index = listeners.firstIndex(where: { $0 === listener }) {
            listeners.remove(at: index)
        }
    }
}

3. SomeListener 类

实现 ManagerStateListener 协议的示例监听器，由 Manager 类持有

class SomeListener : ManagerStateListener {
    
    func stateChanged(to state: Manager.State) {
        /// Do something based on the newly received state
        switch state {
            case .one:
                print("State changed to one")
            case .two:
                print("State changed to two")
            case .three:
                print("State changed to three")
        }
    }
}

希望对大家有帮助。

如何在swift

2 个答案:

1。 ManagerStateListener 协议

2.经理类

3. SomeListener 类