類型 '() -> ()' 不能符合 'View'； 只有結構/枚舉/類類型可以符合協議

Question

我正在運行一個函數來填充費用列表。 我需要運行函數來使用.onAppear(perform: fetchRows)填充列表，以便在視圖出現時列表更新。

Xcode 不喜歡我正在運行一個函數來填充費用列表的事實。 我怎樣才能使這項工作？ 有沒有更好的方法來解決這個問題？

@State var expensesList: [ExpensesList]?

var body: some View {
    
    NavigationView{
        VStack{
                
                if expensesList != nil{
                    
                    
                    List{
                        
                        ForEach(self.expensesList!) {   <-- Type '() -> ()' cannot conform to 'View'; only struct/enum/class types can conform to protocols
                            (log: ExpensesList) in {
                                Button(action: {
                                    self.editExpense = log
                                })
                            
                            ExpenseRow(name: log.expense, date: log.date, amount: log.cost, account: log.account)
                            }
                        }.onDelete(perform: onDelete)
                    }
                }
            }.navigationTitle("Expense List")

struct ExpensesList: Identifiable, Equatable {
    let id: UUID
    let expense: String
    let cost: Double
    let account: String
    let date: Date
}

func fetchRows(){
    Expenses.fetchAllExpensesInDateRange(context: self.context) { (results) in
        guard !results.isEmpty else { return }
        
        self.expensesList = results.map({ (result) -> ExpensesList in
            print(result.id,result.expenseName,result.expenseCost, result.expenseAccount, result.expenseDate)
            return ExpensesList(id: result.id, expense: result.expenseName, cost: result.expenseCost, account: result.expenseAccount, date: result.expenseDate)
        })
    }
}

我用來編輯費用的表格在這里。 如您所見，我使用名為 Expenses 的 Core Data 實體來存儲我的費用對象。

                .sheet(item: $editExpense, onDismiss: {
                    self.editExpense = nil
                })
                {
                    (log: Expenses) in
                    ExpenseDetail(
                        context: self.context,
                        editExpense: log,
                        name: log.expenseName ?? "",
                        amount: String(log.expenseCost),
                        category: log.expenseCategory ?? "",
                        date: log.expenseDate ?? Date(),
                        account: log.expenseAccount ?? "",
                        isMonthly: log.expenseIsMonthly
                    ).environment(\.managedObjectContext, self.context)
                    
                    
                    
                }

Answer 1

您有一個額外的{ after (log: ExpensesList) in {並且您的Button沒有content參數。

請嘗試以下操作（我假設ExpenseRow應該是 Button 的content ）：

ForEach(self.expensesList!) { log in
    Button(action: {
        self.editExpense = log
    }) {
        ExpenseRow(name: log.expense, date: log.date, amount: log.cost, account: log.account)
    }
}

---

請注意，在 SwiftUI 2 中，您可以直接在@ViewBuilder塊中使用控制流語句（如if-let ）：

if let expensesList = expensesList {
    List {
        ForEach(expensesList) { log in
            // ...
        }
    }
}