如何在 Objective-C 中使用 Swift 结构 [英] How to use Swift struct in Objective-C

问题描述

我有一个存储应用程序常量的结构，如下所示:

Simply I have a struct that stores the application constants as below:

struct Constant {

    static let ParseApplicationId = "xxx"
    static let ParseClientKey = "xxx"

    static var AppGreenColor: UIColor {
        return UIColor(hexString: "67B632")
    }
}

这些常量可以通过调用 Constant.ParseClientKey 在 Swift 代码中使用.但在我的代码中，它还包含一些 Objective-C 类.所以我的问题是如何在 Objective-C 代码中使用这些常量?

These constants can be use in Swift code by calling Constant.ParseClientKey for example. But in my code, it also contains some Objective-C classes. So my question is how to use these constants in the Objective-C code?

如果这种声明常量的方式不好，那么创建用于 Swift 和 Objective-C 代码的全局常量的最佳方式是什么?

If this way to declare constants is not good then what is the best way to create global constants to be used in both Swift and Objective-C code?

推荐答案

很遗憾，你不能将 struct 和全局变量暴露给 Objective-C.请参阅文档，其中部分说明:

Sad to say, you can not expose struct, nor global variables to Objective-C. see the documentation, which states in part:

在需要 Objective-C 互操作性时使用类

Use Classes When You Need Objective-C Interoperability

如果您使用需要处理数据的 Objective-C API，或者您需要将数据模型适合在 Objective-C 框架中定义的现有类层次结构中，您可能需要使用类和类继承来建模你的数据.例如，许多 Objective-C 框架公开了您希望子类化的类.

If you use an Objective-C API that needs to process your data, or you need to fit your data model into an existing class hierarchy defined in an Objective-C framework, you might need to use classes and class inheritance to model your data. For example, many Objective-C frameworks expose classes that you are expected to subclass.

到目前为止，恕我直言，最好的方法是这样的:

As of now, IMHO, the best way is something like this:

let ParseApplicationId = "xxx"
let ParseClientKey = "xxx"
let AppGreenColor = UIColor(red: 0.2, green: 0.7, blue: 0.3 alpha: 1.0)

@objc class Constant: NSObject {
    private init() {}

    class func parseApplicationId() -> String { return ParseApplicationId }
    class func parseClientKey() -> String { return ParseClientKey }
    class func appGreenColor() -> UIColor { return AppGreenColor }
}

在 Objective-C 中，你可以像这样使用它们:

In Objective-C, you can use them like this:

NSString *appklicationId = [Constant parseApplicationId];
NSString *clientKey = [Constant parseClientKey];
UIColor *greenColor = [Constant appGreenColor];

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