将泛型委托添加到 Swift 中的基类

Question

理想情况下，我想创建一个BaseViewController 类，该类接受（委托的）协议类型并有一个弱变量作为委托。像这样的：

class BaseViewController<Delegate: AnyObject> {
    weak var delegate: Delegate?

    init(delegate: Delegate) {
        self.delegate = delegate
        super.init(...)
    }
}

然后像这样从视图控制器继承：

protocol MyDelegate: AnyObject { 
    func funcA()
    func funcB()
}  

class SomeViewController: BaseViewController<MyDelegate> {
    func doSomething() {
        delegate?.funcA()
    }
}

编译器抱怨这不起作用：

'BaseViewController' 要求 'MyDelegate' 是类类型

如何解决这个问题以实现我的需要？
在此先感谢:)

Answer 1

那是因为在 swift 协议中不会向它们自己确认，您不能使用“MyProtocol”作为确认协议“MyDelegate”的具体类型

你宁愿做的是

protocol MyDelegate: AnyObject {
    func funcA()
    func funcB()
}

class BaseViewController<Delegate: MyDelegate> {
    weak var delegate: Delegate?

    init(delegate: Delegate) {
        self.delegate = delegate
        super.init(...)
        //keeping OPs code as is
    }
}

class SomeOtherDelegateClass: MyDelegate {
    func funcA() {
        //some code here
    }

    func funcB() {
        //some code here
    }


}

class SomeViewController: BaseViewController<SomeOtherDelegateClass> {
    func doSomething() {
        self.delegate?.funcA()
    }
}

编辑 1：

正如评论中提到的 OP，他试图在 BaseViewController 中引入一个泛型属性，该属性将简单地持有对任何实例的弱引用，该实例的类由 BaseViewController 的子类使用泛型决定/声明，我正在简化上面回答了一下

试试这个

protocol MyDelegate {
    func funcA()
    func funcB()
}

class BaseViewController<Delegate> where Delegate: AnyObject {
    weak var delegate: Delegate?

    init(delegate: Delegate) {
        self.delegate = delegate
        super.init(...)
        //keeping OPs code as is
    }
}

class SomeOtherDelegateClass: MyDelegate {
    func funcA() {
        //some code here
    }

    func funcB() {
        //some code here
    }
}

class SomeViewController: BaseViewController<SomeOtherDelegateClass> {
    func doSomething() {
        self.delegate?.funcA()
    }
}

protocol MyDelegate2 {
    func funcABCD()
}

class SomeOtherDelegateClass2: MyDelegate2 {
    func funcABCD() {
        //some code here
    }
}


class SomeViewController2: BaseViewController<SomeOtherDelegateClass2> {
    func doSomething() {
        self.delegate?.funcABCD()
    }
}

TBH，我真的看不出这种设计有什么好处！可能你需要重新审视代码结构，看看你是否能想出更好的代码结构:)

Answer 2

您应该将您的委托设置为 BaseViewController 中泛型类型 T 的约束：

protocol MyDelegate: AnyObject {
    func funcA()
    func funcB()
}

class Delegated1: MyDelegate {
    func funcA() { print("A1") }
    func funcB() {}
}

class Delegated2: MyDelegate {
    func funcA() { print("A2") }
    func funcB() {}
}

class BaseViewController<T: MyDelegate>: UIViewController {
    var delegate: T?

    func doSomething() {
        delegate?.funcA()
    }
}

class SomeViewController1: BaseViewController<Delegated1> {}
class SomeViewController2: BaseViewController<Delegated2> {}

class TestClass {
    let viewController1: SomeViewController1 = {
        let viewController = SomeViewController1(nibName: nil, bundle: nil)
        viewController.delegate = .init()
        return viewController
    }()

    let viewController2: SomeViewController2 = {
        let viewController = SomeViewController2(nibName: nil, bundle: nil)
        viewController.delegate = .init()
        return viewController
    }()


    // prints:
    // A1
    // A2
    func myFunc() {
        viewController1.doSomething()
        viewController2.doSomething()

    }
}