子类中的Swift覆盖协议方法 [英] Swift override protocol methods in sub classes

问题描述

我有一个基类，它实现了一个符合协议的扩展，如下所示：

I've a base class that implements an extension that conforms to a protocol as below:

protocol OptionsDelegate {
    func handleSortAndFilter(opt: Options)
}

extension BaseViewController: OptionsDelegate {
    func handleSortAndFilter(opt: Options) {
        print("Base class implementation")
    }
}

我有一个继承的子类InspirationsViewController来自BaseViewController。我在扩展中重写协议方法如下：

I've a subclass "InspirationsViewController" that inherits from BaseViewController. And I'm overriding protocol method in the extension as below:

extension InspirationsViewController {
    override func handleSortAndFilter(opt: Options) {
        print("Inside inspirations")
    }
}

当我在子类扩展中覆盖handleSortAndFilter函数时出现错误： 扩展中的疏忽无法覆盖

I'm getting error when I override "handleSortAndFilter" function in subclass extension: "Declerations in extensions cannot override yet"

但是当我实现UITableView数据源和委托方法时，我没有看到类似的问题。

But I'm not seeing similar problem when I implemented UITableView datasource and delegate methods.

如何避免这个错误？

推荐答案

将协议扩展名与where子句一起使用。它有效。

Use protocol extension with where clause. It works.

class BaseViewController: UIViewController {

}

extension OptionsDelegate where Self: BaseViewController {
  func handleSortAndFilter(opt: Options) {
    print("Base class implementation")
  }
}

extension BaseViewController: OptionsDelegate {

}

class InsipartionsViewController: BaseViewController {

}

extension OptionsDelegate where Self: InsipartionsViewController {
  func handleSortAndFilter(opt: Options) {
    print("Inspirations class implementation")
  }
}

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