Swift协议扩展 [英] Swift protocol extension

问题描述

非常感谢文章关于在实例化 UIViewController 或 UIStoryboard 时摆脱使用字符串的问题。

Very much appreciated the article about getting rid of using strings when instantiating UIViewController or UIStoryboard.

尽管有一点我想改变行为。
我没有在此处使用情节提要枚举类来获取情节提要，而是希望此处的类型符合协议。

Though there is one point where I wanted to change the behavior. Instead of giving a Storyboard enum into the class method for getting a storyboard, I wanted a type here that conforms to a protocol.

extension UIStoryboard {
    class func storyboard(storyboard: StoryboardRepresentable, bundle: NSBundle? = nil) -> UIStoryboard {
         return UIStoryboard(name: storyboard.storyboardName, bundle: bundle)
    }
}

protocol StringRawRepresentable: RawRepresentable {
    typealias RawValue = String
    var rawValue: String { get }
}

protocol StoryboardRepresentable {
    var storyboardName: String { get }
}

extension StoryboardRepresentable where Self: StringRawRepresentable {
    var storyboardName: String {
        return self.rawValue
    }
}

enum SomeOtherEnum: String, StoryboardRepresentable {
    case BlaMain
    case BlaSub
    case BlaSomeThing

    var storyboardName: String { return self.rawValue }
}

有了这个（假设您有一些使用此实现的有趣模块），模型本身可以具有符合StoryboardRepresentable的新枚举类型，而不是具有集中式枚举有关所有正在使用的情节提要，从而产生依赖性。

With that (given you have several moduls interesting in using this implementation) the models themselves could have new enum types conforming to StoryboardRepresentable instead of having a centralized enum with knowledge about all storyboards in use and thus creating a dependency.

这是我的问题。尽管我已经在扩展中实现了storyboardName，但是当我在SomeOtherEnum上删除storyboardName时，却遇到了编译器错误，抱怨不符合协议！？

And here is my problem. Though I have implemented the storyboardName in the extension, I got a compiler error complaining about non-protocol conformance when I remove the storyboardName on SomeOtherEnum!?

推荐答案

extension UIStoryboard {
    class func storyboard(storyboard: StoryboardRepresentable, bundle: NSBundle? = nil) -> UIStoryboard {
        return UIStoryboard(name: storyboard.storyboardName, bundle: bundle)
    }
}

protocol StoryboardRepresentable {
    var storyboardName: String { get }
}

extension StoryboardRepresentable where Self: RawRepresentable, Self.RawValue == String {
    var storyboardName: String {
        return self.rawValue
    }
}

enum SomeOtherEnum: String, StoryboardRepresentable {
    case BlaMain
    case BlaSub
    case BlaSomeThing
}

StoryboardRepresentable 现在可以应用于任何 String ，但不要键入 Int 。

StoryboardRepresentable can now be applied to any enum of type String but not to type Int.

这篇关于Swift协议扩展的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！