swift - 如何更新 View 中结构的值

Question

在 SwiftUI 中，我有一个想要保存 View 数据的结构。假设有一个 View ，用户可以在其中创建菜谱。它有一个用于输入配方名称的文本字段，以及用于选择并添加到结构属性中的数组的选项。

我设法制作了该结构并将其引入 View 中，但我无法更改它的值。结构的值应根据用户在 View 上执行的操作以及他们添加到其中的信息进行更新。我制作了一个简单的 View ，在 TextField 中输入的任何内容都将添加到该结构的属性之一中。对于下面的代码，我得到 Cannot allocate to property: 'self' is immutable

struct Recipe: Codable {
let user: Int
var recipeName, createdDate: String
let ingredients: [Ingredient]
let equipment: [[Int]]

enum CodingKeys: String, CodingKey {
    case user = "User"
    case recipeName = "RecipeName"
    case createdDate
    case ingredients = "Ingredients"
    case equipment = "Equipment"
 }
}

struct Ingredient: Codable {
   let ingredient, size: Int
}

查看:

struct ContentView: View {
    var recipe = Recipe(user: 1231, recipeName: "Recipe Name", createdDate: "SomeDate", ingredients: [Ingredient(ingredient: 1, size: 2)], equipment: [[1],[4],[5]])


    var body: some View {
        VStack {
            Text(self.recipe.recipeName)
            Button(action: {
                recipe.recipeName = "New Name" //Cannot assign to property: 'self' is immutable
            }) {
                Text("Change Name")
            }
        }
    }
}

知道如何解决这个问题，以便我可以与结构交互并更新其属性。我也会在其他 View 中使用这个结构变量。

提前致谢

Answer 1

对于所提供的用例，最合适的是使用 View 模型，如下例所示

class RecipeViewModel: ObservableObject {
   @Published var recipe: Recipe
   init(_ recipe: Recipe) {
     self.recipe = recipe
   }
}

所以在 View 中

struct ContentView: View {
    @ObservedObject var recipeVM = RecipeViewModel(Recipe(user: 1231, recipeName: "Recipe Name", createdDate: "SomeDate", ingredients: [Ingredient(ingredient: 1, size: 2)], equipment: [[1],[4],[5]]))


    var body: some View {
        VStack {
            Text(self.recipeVM.recipe.recipeName)
            Button(action: {
                self.recipeVM.recipe.recipeName = "New Name"
            }) {
                Text("Change Name")
            }
        }
    }
}