更新列表中的一行 (SwiftUI)

Posted 2023-02-24

【中文标题】更新列表中的一行 (SwiftUI)

【英文标题】：Update a row in a list (SwiftUI)

【发布时间】：2020-04-07 14:23:52

【问题描述】：

我是编程的早起者，所以我知道从专家的角度来看这个问题可能很荒谬，但我几天后就陷入了这种情况。 在使用另一个按钮使用 TextField 存储项目后，我想通过使用按钮“编辑”（铅笔）来更新一行。

代码如下：

class Food: Hashable, Codable, Equatable 

    var id : UUID = UUID()
    var name : String

    init(name: String) 
        self.name = name
    

    static func == (lhs: Food, rhs: Food) -> Bool 
        return lhs.name == rhs.name
    

    func hash(into hasher: inout Hasher) 
    hasher.combine(name)
    

---

class Manager: ObservableObject 

    let objectWillChange = PassthroughSubject<Void, Never>()

    @Published var shoppingChart: [Food] = []

    init() 

            let milk = Food(name: "Milk")
            let coffee = Food(name: "Coffee")

            shoppingChart.append(milk)
            shoppingChart.append(coffee)        
    

    func newFood(name: String) 
        let food = Food(name: name)
        shoppingChart.insert(food, at: 0)
    

---

struct ContentView: View 

    @ObservedObject var dm : Manager
    @State var isAddFoodOpened = false

    var body: some View 
        VStack 
            List 
                ForEach(self.dm.shoppingChart, id:\.self)  food in
                    HStack 
                    Text(food.name)
                    Image(systemName: "pencil")
                
            

        
            self.buttonAdd
    


    var buttonAdd: some View 
        Button(action: 
            self.isAddFoodOpened.toggle()
        ) 
            Text("Add")
        
        .sheet(isPresented: $isAddFoodOpened) 
            Add(dm: self.dm, fieldtext: "", isAddFoodOpened: self.$isAddFoodOpened)
        
    

---

struct Add: View 

    @ObservedObject var dm : Manager
    @State var fieldtext : String = ""
    @Binding var isAddFoodOpened : Bool

    var body: some View 
        VStack 
        TextField("Write a food", text: $fieldtext)
        buttonSave
    
    

    var buttonSave : some View 
        Button(action: 
            self.dm.newFood(name: self.fieldtext)
            self.isAddFoodOpened = false
        ) 
            Text("Save")
        
    

【问题讨论】：

只是一个不相关的注释，如果与 Food 类的其他对象相比，使 food 对象独一无二的是名称，那么将其设为 id 属性并避免创建像：var id: String name 或在你的初始化中设置id。所以，当你需要食物的 id 时，只需返回 name。

【参考方案1】：

@ObservedObject var dm : Manager 对象永远不会被初始化。

尝试像这样在 ContentView 中初始化 dm：

@ObservedObject var dm = Manager()

【参考方案2】：

好的，如果我理解正确，您想使用“编辑”按钮更新/编辑一行。 这样就可以了：

struct ContentView: View 

@ObservedObject var dm : Manager
@State var isAddFoodOpened = false
@State var isEditOpened = false
@State var fieldtext : String = ""

var body: some View 
    VStack 
        List 
            ForEach(0..<self.dm.shoppingChart.count, id:\.self)  i in
                HStack 
                    Text(self.dm.shoppingChart[i].name)
                    Button(action:  self.isEditOpened.toggle() ) 
                        Image(systemName: "pencil")
                    .sheet(isPresented: self.$isEditOpened) 
                        TextField(self.dm.shoppingChart[i].name, text: self.$fieldtext, onEditingChanged:  _ in
                            self.dm.shoppingChart[i].name = self.fieldtext
                        )
                    
                
            
        
        self.buttonAdd
    


var buttonAdd: some View 
    Button(action: 
        self.isAddFoodOpened.toggle()
    ) 
        Text("Add")
    
    .sheet(isPresented: $isAddFoodOpened) 
        Add(dm: self.dm, fieldtext: "", isAddFoodOpened: self.$isAddFoodOpened)
    

【讨论】：

如何保存 TextField 的更改并返回 Content View？

TextField的变化保存在：self.dm.shoppingChart[i].name = self.fieldtext