Swift无法通过委托调用协议方法 [英] Swift can't call protocol method via delegate

问题描述

我有两节课。一个类名为 ViewController ，另一个类名为 TabView 。

I have two classes. One class is named ViewController and the other class is named TabView.

我的目标是从ViewController调用一个函数 changeTab（），它位于TabView类中。

My goal is to call a function changeTab() which is inside the TabView class from the ViewController.

不知怎的，我遇到了麻烦，因为每次我的代表都是 nil 。

Somehow I am having trouble with it because everytime my delegate is nil.

这是我的ViewController的代码：

protocol TabViewProtocol: class {
    func changeTab() 
}

class ViewController: NSViewController {
    // delegate
    weak var delegateCustom : TabViewProtocol?

    override func viewDidLoad() {
        print(delegateCustom) // outputs "nil"
    }

    buttonClickFunction() {
        print(delegateCustom) // outputs "nil"
        delegateCustom?.changeTab() // doesn't work
    }
}

以下是我的TabView代码：

class TabView: NSTabViewController, TabViewProtocol {

    let myVC = ViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        myVC.delegateCustom = self
    }

    func changeTab() {
        print("test succeed")
    }
}

有人可以解释一下我做错了什么吗？ - 我是代表和协议的新手...

Can someone explain me what I am doing wrong? - I am new to delegates and protocols...

推荐答案

您错误地使用了委托模式。很难说你想要为哪个控制器定义协议以及你想采用哪个控制器 - 但这是一种可行的方法。

You are using the delegate pattern wrongly. It is hard to tell which controller you want to define the protocol for and which one you want to adopt it - but here is one possible way.

// 1. Define your protocol in the same class file as delegate property.
protocol TabViewProtocol: class {
    func changeTab() 
}

// 2. Define your delegate property
class ViewController: NSViewController {
    // delegate
    weak var delegateCustom : TabViewProtocol?

    override func viewDidLoad() {
        // It should be nil as you have not set the delegate yet.
        print(delegateCustom) // outputs "nil"
    }

    func buttonClickFunction() {
        print(delegateCustom) // outputs "nil"
        delegateCustom?.changeTab() // doesn't work
    }
}

// 3. In the class that will use the protocol add it to the class definition statement

class TabView: NSTabViewController, TabViewProtocol {

    let myVC = ViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        myVC.delegateCustom = self

        // Should output a value now
        print(myVC.delegateCustom) // outputs "self"
    }

    func changeTab() {
        print("test succeed")
    }
}

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