SwiftUI: "Property initializers run before 'self' is available" 在@AppStorage 使用

Question

我是 Swift 的新手，想解决这个问题。我希望，当我关闭并返回应用程序时，选择器中的货币会被保存。（通过@AppStorage）但是我无法使用我想到的任何东西来将$currency 定义为@AppStorage 中的$cur。谢谢你的帮助！这里的代码：

//Settings
struct SettingsView: View {

@State private var currency = "$"
var currencies = ["$", "€", "¥", "£"]
@AppStorage("name") var name = ""
@AppStorage("cur") var cur = "\($currency)"
//Cannot use instance member '$currency' within property initializer; property initializers run before 'self' is available

var body: some View {
    NavigationView {
        
        Form {
            Section(header: Text("Your name")) {
                TextField("Tim", text: $name)
            }
            
            Section(header: Text("Your currency")) {
                Picker(selection: $currency, label: Text("Your Currency")) {
                    ForEach(currencies, id: \.self) {
                        Text([=11=])
                    }
                }
                .pickerStyle(SegmentedPickerStyle())
            }
        }
        
    }
    .navigationTitle("Settings")
    }
}

Answer 1

定义cur时不能引用$currency。这是 Swift 的限制。很明显，货币已经有一个值，但是 Swift 不会让你使用它，直到初始化程序完成自我设置。这与 AppStorage 无关——这是一条规则，属性初始化器不能引用其他（非静态）属性。

所以，这个

@State private var currency = "$"
@AppStorage("cur") var cur = "\($currency)"

可能是

@State private var currency = "$"
@AppStorage("cur") var cur = "$" // set it to the same value

或

private static let dollar = "$"

@State private var currency = SettingsView.dollar
@AppStorage("cur") var cur = SettingsView.dollar

SwiftUI: "Property initializers run before 'self' is available" 在@AppStorage 使用

SwiftUI: "Property initializers run before 'self' is available" in @AppStorage use

xcode

properties

picker

swift

swiftui