类型 '() -> ()' 不能符合 'View'；只有结构/枚举/类类型可以符合协议

Question

我正在运行一个函数来填充费用列表。我需要运行该函数以使用.onAppear(perform: fetchRows) 填充列表，以便在视图出现后立即更新列表。

Xcode 不喜欢我正在运行一个函数来填充费用列表。我怎样才能使这项工作？有没有更好的方法来解决这个问题？

@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)
        })
    }
}

我用来编辑费用的表格在这里。如您所见，我使用一个名为 Expenses 的核心数据实体来存储我的费用对象。

                .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

在(log: ExpensesList) in { 之后有一个额外的{，而你的Button 没有content 参数。

改用以下方法（我假设ExpenseRow 应该是按钮的content）：

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

---

请注意，在 SwiftUI 2 中，您可以直接在 @ViewBuilder 块中使用控制流语句（如 if-let）：

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