如何将 Parent 委派给多个不同的孩子？

Question

我有这个方案：

家庭控制器
- 导航控制器
  - Step1（NavigationController 的child）
  - Step2（NavigationController 的child）

我的问题是我不知道如何将信息从 Parent 传递给所有不同的 childs，因为当我将委托分配给 childs 时，总是需要最后一个一。因此，如果我调用委托，只有最后添加的 child 会收到信息

一些基本代码：

class HomeController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        addSubview(showSteps)
    }
    @objc func showSteps() {
        let controller = NavigationController()
        self.present(controller, animated: true, completion: nil)
    }
}


protocol UserProtocol: AnyObject {
    func userHasChanged(_ user: User?)
}


class NavigationController: UIViewController {

    var user: User?
    weak var delegate: UserProtocol?
    
    override func viewDidLoad() {
        
        // all step childs are differents
        let step1 = Step1()
        addStep(step: step1)
        delegate = step1
        
        let step2 = Step2()
        addStep(step: step2)
        delegate = step2
        
        let step3 = Step3()
        addStep(step: step3)
        delegate = step3
        
        let step4 = Step4()
        addStep(step: step4)
        delegate = step4
        
    }
    
    func addStep(step: UIViewController){
        self.addChild(step)
        step.willMove(toParent: self)
        view.addSubview(step.view)
        step.didMove(toParent: self)
    }
    
    func userHasChanged(_ user: User?){
        // this observe new user data from firebase
        Service.shared.fetchUserData(uid: "XXX") { user in
            self.user = user
            // send new data to childs
            // ONLY SEND TO CHILD4, (THE LAST ONE OBVIOUSLY)
            self.delegate?.userHasChanged(user)
        }
    }

}

// that is a child example
class Step1: UIViewController, UserProtocol {
    
    var user: User?
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    func tripHasChanged(_ new_user: User?) {
        print("changed1")
        self.user = new_user
    }

}

class Step2: UIViewController, UserProtocol {
    
    var user: User?
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    func tripHasChanged(_ new_user: User?) {
        print("changed2")
        self.user = new_user
    }

}

class Step3: UIViewController, UserProtocol {
    
    var user: User?
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    func tripHasChanged(_ new_user: User?) {
        print("changed3")
        self.user = new_user
    }

}

class Step4: UIViewController, UserProtocol {
    
    var user: User?
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    func tripHasChanged(_ new_user: User?) {
        print("changed4")
        self.user = new_user
    }

}

*只打印“changed4”

我的问题：

我怎样才能通过一个委托（也许是数组？）将数据发送到所有不同的 child？。有可能，属于好的做法？

谢谢！

Answer 1

您可以创建委托数组...但这实际上不是委托/协议设计模式。

您也可以采用 NotificationCenter addObserver / post 通知方法...但这更适合多个对象，这些对象不一定在当前 class.

对于您的情况 - 多个子视图控制器都需要基于同一事件“做某事”，更好的方法可能是创建一个“基础”视图控制器并使每个“步骤”子class那个基地的。

这是一个简单的例子...

// this is our "Step" base view controller
//  creates the "user" property
//  defines the "userHasChanged()" method
class StepBaseViewController: UIViewController {

    var user: String?
    func userHasChanged(_ new_user: String) {
        user = new_user
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // we can do anything that may be
        //  "common" to all "Steps"
    }

}

您创建 StepBaseViewController 的子 class 的任何视图控制器现在将具有 user 属性和处理 userHasChanged 的默认方法。此外，可以在 viewDidLoad().

中设置对步骤“通用”的任何内容（例如标签、按钮等 UI 元素）

现在你的第 4 个“步骤”class 变成：

class Step1: StepBaseViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setup specific to this "Step"
    }
    override func userHasChanged(_ new_user: String) {
        super.userHasChanged(new_user)
        print("User changed to:", self.user, "in:", self)
        // do something specific to Step 1
    }
}
class Step2: StepBaseViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setup specific to this "Step"
    }
    override func userHasChanged(_ new_user: String) {
        super.userHasChanged(new_user)
        print("User changed to:", self.user, "in:", self)
        // do something specific to Step 2
    }
}
class Step3: StepBaseViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setup specific to this "Step"
    }
    override func userHasChanged(_ new_user: String) {
        super.userHasChanged(new_user)
        print("User changed to:", self.user, "in:", self)
        // do something specific to Step 3
    }
}
class Step4: StepBaseViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setup specific to this "Step"
    }
    override func userHasChanged(_ new_user: String) {
        super.userHasChanged(new_user)
        print("User changed to:", self.user, "in:", self)
        // do something specific to Step 4
    }
}

这里是您的 NavigationController 的修改版本，展示了如何使用此方法：

class NavigationController: UIViewController {

    // we'll simulate the user changing
    //  so on first tap the user will become "User 1"
    //  on next tap user will become "User 2"
    //  on next tap user will become "User 3"
    // and so on
    var n: Int = 0
    var user: String = ""
    
    override func viewDidLoad() {
        
        // all step childs are differents
        let step1 = Step1()
        addStep(step: step1)
        
        let step2 = Step2()
        addStep(step: step2)
        
        let step3 = Step3()
        addStep(step: step3)
        
        let step4 = Step4()
        addStep(step: step4)
        
    }
    
    func addStep(step: UIViewController){
        self.addChild(step)
        step.willMove(toParent: self)
        view.addSubview(step.view)
        step.didMove(toParent: self)
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // simulate the "user changed" event
        n += 1
        self.user = "User \(n)"
        self.children.forEach { child in
            if let vc = child as? StepBaseViewController {
                vc.userHasChanged(self.user)
            }
        }
    }

}

加载 NavigationController 后，点击 3 次会导致此调试控制台输出：

User changed to: Optional("User 1") in: <MyProj.Step1: 0x7fbd7a21caf0>
User changed to: Optional("User 1") in: <MyProj.Step2: 0x7fbd7a21c480>
User changed to: Optional("User 1") in: <MyProj.Step3: 0x7fbd7a21d480>
User changed to: Optional("User 1") in: <MyProj.Step4: 0x7fbd7a21dca0>
User changed to: Optional("User 2") in: <MyProj.Step1: 0x7fbd7a21caf0>
User changed to: Optional("User 2") in: <MyProj.Step2: 0x7fbd7a21c480>
User changed to: Optional("User 2") in: <MyProj.Step3: 0x7fbd7a21d480>
User changed to: Optional("User 2") in: <MyProj.Step4: 0x7fbd7a21dca0>
User changed to: Optional("User 3") in: <MyProj.Step1: 0x7fbd7a21caf0>
User changed to: Optional("User 3") in: <MyProj.Step2: 0x7fbd7a21c480>
User changed to: Optional("User 3") in: <MyProj.Step3: 0x7fbd7a21d480>
User changed to: Optional("User 3") in: <MyProj.Step4: 0x7fbd7a21dca0>

如何将 Parent 委派给多个不同的孩子？

How to Delegate from Parent to Multiple Different Childs?

delegates

protocols

ios

swift