如何在SwiftUI内购退款请求中捕获并展示错误信息

我正在修改Apple官方《Food Truck: Building a SwiftUI Multiplatform App》示例中的退款请求逻辑，需要捕获退款请求错误。但Apple的示例未展示错误捕获方法，给学习者造成了困扰。

目前我能在代码标注“catch refund errors here”的result中看到错误，打印信息如下：

refund error Binding<Optional>(transaction: SwiftUI.Transaction(plist: []), location: SwiftUI.StoredLocation<Swift.Optional<Swift.Error>>, _value: nil)
failure(StoreKit.Transaction.RefundRequestError.duplicateRequest)
Transaction.RefundError RefundRequestError

我的需求是：如何将错误（比如duplicateRequest）的localizedDescription展示到Alert中？
问题在于成功分支未使用do/catch块就直接跳转，我尝试用error、gotError存储错误，但不清楚result的类型。相关代码如下：

struct RefundView: View {
    @State private var recentTransactions: [StoreKit.Transaction] = []
    @State private var selectedTransactionID: UInt64?
    @State private var refundSheetIsPresented = false
    
    @State private var error: Error?
    @State private var refundError: Bool = false
    @State var gotError: String = ""

    @Environment(\.dismiss) private var dismiss

    var body: some View {
            
            List(recentTransactions, selection: $selectedTransactionID) { transaction in
                TransactionRowView(transaction: transaction)
            }
            .safeAreaInset(edge: .bottom) {
                VStack(spacing: 0) {
                    Text("Select a purchase to refund")
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                        .padding()
                    Button {
                        refundSheetIsPresented = true
                    } label: {
                        Text("Request a refund")
                            .bold()
                            .padding(.vertical, 5)
                            .frame(maxWidth: .infinity)
                    }
                    .buttonStyle(.borderedProminent)
                    .padding([.horizontal, .bottom])
                    .disabled(selectedTransactionID == nil)
                }
            }
            
            .task { @MainActor in
                for await transaction in StoreKit.Transaction.all {
                    recentTransactions.append(transaction.unsafePayloadValue)
                }
            }
            .refundRequestSheet(
                for: selectedTransactionID ?? 0,
                isPresented: $refundSheetIsPresented
            ) { result in
                if case .success(.success) = result {
                    dismiss()
                }
                // ******* catch refund errors here *******
                self.error = error
                refundError.toggle()
              //  $gotError = result
                
                print("refund error \($error)")
                print(result)
                print("Transaction.RefundError \(Transaction.RefundRequestError)")
                
            }
        .navigationTitle("Refund Purchase")
        .alert("Refund error: \(gotError)", isPresented: $refundError, actions: {})
    }
}

1. 明确result的类型 #

refundRequestSheet的回调参数result类型是Result<StoreKit.Transaction.RefundRequestStatus, Error>：

• .success的关联值是RefundRequestStatus枚举，包含.success（退款请求提交成功）、.userCancelled（用户取消操作）两种情况
• .failure的关联值就是具体的Error对象，比如你遇到的RefundRequestError.duplicateRequest

2. 正确解析错误并触发Alert #

修改回调逻辑，通过模式匹配捕获错误，提取localizedDescription并更新状态变量：

.refundRequestSheet(
    for: selectedTransactionID ?? 0,
    isPresented: $refundSheetIsPresented
) { result in
    switch result {
    case .success(let status):
        if status == .success {
            dismiss() // 退款请求提交成功，关闭页面
        }
        // 用户取消操作时可根据需求添加提示，或不做处理
    case .failure(let error):
        gotError = error.localizedDescription
        refundError = true // 触发错误Alert
    }
}

3. 优化Alert显示效果 #

调整Alert代码，让错误信息展示更清晰：

.alert("退款失败", isPresented: $refundError) {
    Button("确定", role: .cancel) {}
} message: {
    Text(gotError)
}

4. 清理无效代码 #

删除原代码中self.error = error这类无效赋值，以及$gotError = result这种类型不匹配的错误写法。

内容的提问来源于stack exchange，提问作者Galen Smith