我是SwiftUI的新手，并希望在我正在开发的项目中获得帮助。
我无法在结构外部引用@published值。
使用以下命令，所有值都可以在结构中正常运行：
@ObservableObject
@Publihsed
@ObservedObject
我在ContentView中有一个结构，该结构链接到另一个我要显示数量和成本的视图。
我已经尝试了各种方法来访问值，如在结构NewOrders中所见，但是我一直得到零，而没有获得更新后的值。
我错过了一步还是执行了错误的代码？
预先感谢
class MealOrders: ObservableObject {
//Jollof Rice - Published
@Published var jollof = 0
//Swallow - Published
@Published var swallow = 0
//Pepper Soup - Published
@Published var pepperSoup = 0
}
struct ContentView: View {
var body: some View {
VStack {
NavigationView {
Section {
VStack(alignment: .leading) {
NavigationLink(destination: MenuOption()) {
Text("Meal Options")
}
Spacer()
.frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight:
.infinity, alignment: .topLeading)
}.padding() //Vstack End
}
Section {
VStack {
Image("africanfoods")
.resizable()
.frame(width: 275.0, height: 250.0)
.clipShape(Circle())
.overlay(Circle().stroke(Color.black, lineWidth: 5))
.scaledToFit()
}
} //Section End
Section { //Social Media
VStack {
Spacer()
HStack {
Spacer()
Image("facebook")
.resizable()
.frame(width:40, height: 40)
.scaledToFit()
.padding()
Image("instergram")
.resizable()
.frame(width:40, height: 40)
.scaledToFit()
.padding()
Image("youtube")
.resizable()
.frame(width:40, height: 40)
.scaledToFit()
.padding()
Image("twitter")
.resizable()
.frame(width:40, height: 40)
.scaledToFit()
.padding(.horizontal, 50)
}
} //Vstack End
} //Social Media
.navigationBarTitle(Text("African Foods Center"))
} //NavView End
} //VStack End
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
struct MenuOption: View {
//Object Observed Declarations
@ObservedObject var meals = MealOrders()
//Meal Prices
@State private var jolloRiceUnitCost = 14.95 //Jollof Rice Unit Cost
@State private var swallowUnitCost = 12.50 //Swallow Unit Cost
@State private var pepperSoupUnitCost = 13.50 //Pepper Soup Unit Cost
@State private var deliveryCost = 5.99 //Delivery Cost
@State private var menuItem = 0
var menuItems = ["Rice Meals", "Swallow Meals", "Pepper Soups"]
//Meals Calculator
var calculateMeal: Double {
var orderCost = 0.0
//Jollof Rice
if menuItems[menuItem] == "Rice Meals" {
orderCost = self.jolloRiceUnitCost * Double(self.meals.jollof)
return orderCost
//Swallow - Pounded Yam / Eba
} else if menuItems[menuItem] == "Swallow Meals" {
orderCost = self.swallowUnitCost * Double(self.meals.swallow)
} else if menuItems[menuItem] == "Pepper Soups" {
orderCost = self.pepperSoupUnitCost * Double(self.meals.pepperSoup)
}
return orderCost
}
var body: some View {
VStack(alignment: .leading) {
Section(header: Text("Select Meal").padding(.horizontal, 25)) {
Picker("Select Item", selection: $menuItem) {
ForEach(0 ..< menuItems.count) {
Text(self.menuItems[$0])
}
}.pickerStyle(SegmentedPickerStyle())
.padding(.horizontal, 25)
if menuItems[menuItem] == "Rice Meals" {
Text("Rice Meals:")
.foregroundColor(.black)
.padding(.horizontal, 25)
Spacer().frame(height:20)
`Text("Rice meals consist of Jollof Rice, Rice and Stew, Fried
Rice. You can option in meat, fish and or plantain with any of the meals")`
.foregroundColor(.blue)
.lineLimit(nil)
.padding(.horizontal, 25)
Spacer().frame(height:60)
//Insert image - Jollof Rice
Image("jollofRice")
.resizable()
.frame(width:250, height: 250)
.scaledToFit()
.border(Color.black, width: 4)
.padding(.horizontal, 100)
Spacer().frame(height:20)
HStack {
Stepper("Quantity (Max 5)",value: $meals.jollof, in: 0...5)
.padding(.horizontal, 45)
Text("\(meals.jollof): £\(calculateMeal, specifier: "%.2f")")
.padding()
}.padding()
Section { //Button Order
VStack {//Add Stepper for Quantity
Spacer()
HStack(alignment: .center, spacing: 140) {
Spacer()
Button(action: {}) {
NavigationLink(destination: Text("Jollof:: \(meals.jollof), £\(calculateMeal, specifier: "%.2f")")) {
Text("Create Order")
.font(.system(size: 14))
.padding()
.background(Color.blue)
.foregroundColor(.white)
.cornerRadius(6)
}.padding()
Spacer()
}
}
} //Vstack End
} //Button Section End
} else if menuItems[menuItem] == "Swallow Meals" {
Text("Swallow")
.foregroundColor(.green)
.padding(.horizontal, 25)
Spacer().frame(height:20)
`Text("Swallow is the colloqual word for Pounded Yam, Eba, Fufu or Amala. This is complemented with soups, such as Egusi, Okra etc. You could have this meal with either meat or fish")`
.foregroundColor(.blue)
.lineLimit(nil)
.padding(.horizontal, 25)
Spacer().frame(height:60)
//Inset Image
Image("poundedYamEgusi")
.resizable()
.frame(width:250, height:250)
.scaledToFit()
.border(Color.black, width: 4)
.padding(.horizontal, 100)
HStack {//Add Stepper for Quantity
Stepper("Quantity (Max 5)",value: $meals.swallow, in: 0...5)
.padding(.horizontal, 45)
Text("\(meals.swallow): £\(calculateMeal, specifier: "%.2f")")
.padding()
}.padding()
//Insert Order Button
Section {
VStack {
Spacer()
HStack(alignment: .center, spacing: 140) {
Spacer()
Button(action: {}) {
NavigationLink(destination: Text("Swallow: \(meals.swallow), £\(calculateMeal, specifier: "%.2f")")) {
Text("Create Order")
.font(.system(size: 14))
.padding()
.background(Color.blue)
.foregroundColor(.white)
.cornerRadius(6)
}.padding()
Spacer()
}
}
} //VStack End
} //Section End
} else if menuItems[menuItem] == "Pepper Soups" {
Text("Pepper Soup")
.foregroundColor(.red)
.padding(.horizontal, 25)
Spacer().frame(height:20)
`Text("Pepper soup is normally taken after one has had either Pounded Yam or rice meals. Depending on the audeience, the soup can be lightly spicy to very hot. Pepper soup can be had with either fish or meat")`
.foregroundColor(.blue)
.lineLimit(nil)
.padding(.horizontal, 25)
Spacer().frame(height:60)
//Insert Image
Image("pepperSoupYam")
.resizable()
.frame(width:250, height:250)
.scaledToFit()
.border(Color.black, width: 4)
.padding(.horizontal, 100)
HStack {//Add Stepper Quantity for Pepper Soup
Stepper("Quantity (5 Max)",value: $meals.pepperSoup, in: 0...5)
.padding(.horizontal, 45)
Text("\(meals.pepperSoup): £\(calculateMeal, specifier: "%.2f")")
.padding()
}.padding()
//Inset Order Button
Section {
VStack {
Spacer()
HStack(alignment: .center, spacing: 140) {
Spacer()
Button(action: {}) {
NavigationLink(destination: NewOrders()) {
Text("Create Order")
.font(.system(size: 14))
.padding()
.background(Color.blue)
.foregroundColor(.white)
.cornerRadius(6)
}.padding()
Spacer()
}
}
}
}
}
Spacer()
}.font(.system(size: 14))
.foregroundColor(.purple)
} //Vstack Ending
} //View Ending
}
//This sis going to be the Orders Struct
struct NewOrders: View {
@ObservedObject var orderUpdatedV2 = MealOrders()
@State private var orderUpdate = MenuOption().meals.jollof
var body: some View {
//let mealsU: ContentView
NavigationView{
VStack {
List {
Text("")
}
}
}.navigationBarTitle("Meal Order")
}
}
答案 0 :(得分：0)
下面的这一行是不正确的，因为会创建新值，这就是为什么您拥有nil
@State private var orderUpdate = MenuOption().meals.jollof
相反，您需要拥有（据我了解您的代码）
@Binding var orderUpdate: Int
并通过它代替创建
NavigationLink(destination: NewOrders(orderUpdate: $meals.jollof)) {
注意：这是个主意，我不确定复制/粘贴是否可行，因为您的代码快照无法在我身边编译。