swift - SwiftUI - 不清楚如何使用异步方法处理警报

Question

如果用户点击它，我必须在视图上显示警报。

我的警报取决于几种情况：

1. 商品已购买。显示项目。
2. 物品尚未购买。显示一个提醒，告诉用户必须购买该物品。此警报必须显示两个按钮，确定购买，取消取消。
3. 用户点击购买商品。
4. 购买成功，出示商品。
5. 购买失败，显示错误。

我就是这样做的。

  class AlertDialog {
    enum SelectedType {
      case none
      case purchase
      case mustBePurchased
      case purchaseError
    }
    
    var selectedType:SelectedType = .none

  }


struct FilteredListItem: View {

  @State var showAlert: Bool = false
  private var alertDialog:AlertDialog?

 var body: some View {
      Text(item.termLowerCase)
        .font(fontItems)
        .foregroundColor(.white)
        .onTapGesture {
          DispatchQueue.main.async {            
            appStoreWrapper.verifyPurchase(productID: item.package!)
            { // run if purchased
              purchased = true
            } runIfNotPurchased: {
              purchased = false
              alertDialog!.selectedType = .mustBePurchased
              showAlert = true
            } 
          }
        }
    .alert(isPresented: $showAlert) {       
      if alertDialog!.selectedType  == .purchase {
        appStoreWrapper.purchase(productID: item.package!) {
          // run if purchased
          purchased = true
        } runIfPurchaseFailed: { (error) in
          alertDialog!.selectedType = .purchaseError
          appStoreWrapper.purchaseError = error
          showAlert = true
        }
        
      } else if alertDialog!.selectedType  == .purchaseError {
        let primaryButton = Alert.Button.default(Text("OK")) {
          showAlert = false
        }
        return Alert(title: Text(appStoreWrapper.makeString("ERROR")),
                     message: Text(appStoreWrapper.purchaseError),
                     dismissButton: primaryButton)
        
      }
    
      
      let dismissButton = Alert.Button.default(Text(appStoreWrapper.makeString("CANCEL"))) {
        showAlert = false
      }
      
      let primaryButton = Alert.Button.default(Text("OK")) {
        appStoreWrapper.purchase(productID: item.package!) {
          // run if purchased
          purchased = true
        } runIfPurchaseFailed: { (error) in
          appStoreWrapper.purchaseError = error
          alertDialog!.selectedType = .purchaseError
          showAlert = true
          print(erro)
        }
      }
      
      return Alert(title: Text(appStoreWrapper.makeString("ERROR")),
                   message: Text(appStoreWrapper.purchaseError),
                   primaryButton: primaryButton,
                   secondaryButton: dismissButton)
    }

这是我的问题：修饰符.alert(isPresented: $showAlert)期望Alert()返回一个，对吗？但我有这些异步方法

appStoreWrapper.verifyPurchase(productID: item.package!)
        { // run if purchased }, 
        runIfNotPurchased: { }

不能将任何内容返回给警报修饰符。我怎么做？我做的对吗？

标签： swiftswiftui

Answer 1

您的代码中有很多内容，您没有发布 appStoreWrapper 的代码，但这里有一些代码应该能够为您指明正确的方向。

供参考：

• 您可以将 Button 与 Action 一起使用，而不是将 Text 与 .onTapGesture 一起使用

• .Alert 中的代码只能用于获取警报。您不应该在 .Alert 闭包中执行其他操作。

   struct FilteredListItem: View {
  
       @State var showAlert: Bool = false
       private var alertDialog: AlertDialog?
  
       var body: some View {
           Button(action: {
               verifyItem()
           }, label: {
               Text("ITEM NAME")
                   .foregroundColor(.white)
           })
           .accentColor(.primary)
           .alert(isPresented: $showAlert, content: {
               getAlert()
           })
       }
  
       func verifyItem() {
           // FUNCTION TO VERIFY ITEM HERE
           var success = true //appStoreWrapper.verifyPurchase...
  
           if success {
               // Handle success
           } else {
               alertDialog?.selectedType = .mustBePurchased
               showAlert.toggle()
           }
       }
  
       func purchaseItem() {
           // FUNCTION TO PURCHASE ITEM HERE
           var success = true //appStoreWrapper.purchase...
  
           if success {
               // Handle success
           } else {
               alertDialog?.selectedType = .purchaseError
               showAlert.toggle()
           }
       }
  
       func getAlert() -> Alert {
           guard let dialog = alertDialog else {
               return Alert(title: Text("Error getting alert dialog."))
           }
  
           switch dialog.selectedType {
           case .purchaseError:
               return Alert(
                   title: Text("Error purchasing item."),
                   message: nil,
                   dismissButton: .default(Text("OK")))
           case .mustBePurchased:
               return Alert(
                   title: Text("Items have to be purchased."),
                   message: nil,
                   primaryButton: .default(Text("Purchase"), action: {
                       purchaseItem()
                   }),
                   secondaryButton: .cancel())
           case .none, .purchase:
               return Alert(title: Text("Purchased!"))
           }
       }
  
   }