如何对依赖自动语法协议的字符串使用插值？

Question

我正在尝试解决一个看似简单的问题：在 SwiftUI Text 视图中向用户显示免费试用条款。我有一个设置为 "Week" 的单位字符串和一个可以从 1 切换到 2 的 value。为了处理复数，我利用了 iOS 15 上的自动语法协议。我在我的 Localizable.strings 文件中准备好字符串，如下所示：

"Subscription period: %lld %@" = "^[%lld ^[%@](grammar: { partOfSpeech: \"noun\" })](inflect: true)";

为了构建字符串，我需要使用字符串插值来添加单词 'free'。我知道在字符串文件中添加单词可以解决问题，但我不想那样做。我想普遍使用该字符串，不一定与免费试用有关。我不明白为什么我不能调用一些 init，给它传递一个键，然后得到一个我可以随意插入的纯字符串。我已经尝试了很多在所附代码片段中展示的方法。找不到字符串，或者未应用自动语法协议。似乎有 String.LocalizationValue.StringInterpolation 结构，但我不知道如何使用它，因为没有任何文档。我究竟做错了什么？如果有任何帮助，我将不胜感激！

struct ContentView: View {
    /// This value mimics what **StoreKit 2** returns for `Product.SubscriptionPeriod.Unit` in its `localizedDescription` on iOS 15.4.
    let unit = "Week"
    
    @State var value = 1
    
    var key: LocalizedStringKey {
        "Subscription period: \(value) \(unit)"
    }
    
    var plainStringKey: String {
        "Subscription period: \(value) \(unit)"
    }
    
    var body: some View {
        Form {
            Section {
                // Works fine without string interpolation.
                Text(key)
                    .foregroundColor(.green)
                
                // `NSLocalizedString` doesn't work and it shouldn't as per its docs.
                Text("\(NSLocalizedString(plainStringKey, comment: "")) free")
                    .foregroundColor(.red)
                
                // Doesn't see the string.
                Text("\(String(localized: String.LocalizationValue(stringLiteral: plainStringKey))) free")
                    .foregroundColor(.red)
                
                // This way also doesn't see the string, which is strange, because it should be just like the following way, which does see the string.
                Text("\(String(localized: String.LocalizationValue.init(plainStringKey))) free")
                    .foregroundColor(.red)
                
                // Sees the string (only if I pass literal, not the plainStringKey property), but doesn't apply automatic grammar agreement.
                Text("\(String(localized: String.LocalizationValue("Subscription period: \(value) \(unit)"))) free")
                    .foregroundColor(.red)
                
                
                // MARK: Bad solution:
                /*
                 - Doesn't work with Dynamic Type properly
                 - You have to approximate horizontal spacing
                 */
                
                HStack(spacing: 3) {
                    Text("Subscription period: \(value) \(unit)")
                        .textCase(.lowercase)
                    Text("free")
                }
                .foregroundColor(.orange)
            }
            
            Section {
                Stepper(value: $value, in: 1...2) {
                    Text("Value: \(value)")
                }
            }
        }
    }
}

您可以下载示例项目here。

Answer 1

其实我和这段代码非常接近：

Text("\(String(localized: String.LocalizationValue("Subscription period: \(value) \(unit)"))) free")

但是使用 String(localized:) 是不正确的。我猜是因为自动语法协议使用markdown，这是AttributedString的特权。我们应该使用 AttributedString(localized:)。但即便如此，它也不会屈折变化，因为 Foundation 中显然存在错误。但是一旦打上补丁，它就会发挥作用。

这是正确的解决方案：

func freeTrialDuration() -> Text {
    // Use plain string.
    let duration: String = "^[\(value) ^[\(unit.lowercased())](grammar: { partOfSpeech: \"noun\" })](inflect: true)"
    // Use the following way to get the localized string.
    let localizedDuration = AttributedString(localized: String.LocalizationValue(duration))
    
    return Text("\(localizedDuration) free")
}

如何对依赖自动语法协议的字符串使用插值？

How to use interpolation with strings that rely on automatic grammar agreement?

string

nslocalizedstring

ios

swift

swiftui