objective-c - 如何在 Objective-C 中使用 Swift 结构

Question

我有一个存储应用程序常量的结构，如下所示:

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？

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？

Answer 1

遗憾的是，您不能将 struct 或全局变量暴露给 Objective-C。见 the documentation ，其中部分说明:

Use Classes When You Need Objective-C Interoperability

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:

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:

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