无法将选取器结果保存到 UserDefaults [英] Unable to Save Picker Result to UserDefaults

问题描述

我正在尝试将选择器的结果保存为用户默认值.用户默认保存操作发生在类 UserData 中，通过方法 saveBase.

I am trying to save the result of a picker to user defaults. The user default save operation occurs in the class UserData via method saveBase.

我已经用按钮成功地尝试了类似的技术，但是我在选择器之后的调用给出了著名的错误:

I have tried a similar technique successfully with a button but my call after the picker gives the famous error:

类型()"不能符合视图.

Type '()' cannot conform to view.

struct aboutView: View {

    @EnvironmentObject var userData: UserData

    @State private var baseEntry: Int = 0
    
    let base = ["Level 1", "Level 2","Level 3","Level 4"]
    
    var body: some View {
                
        Text("comment")
        Text("comment")
        Text("comment")

           
        Section {
            Picker(selection: $baseEntry, label: Text("Select Base >")) {
                ForEach(0 ..< self.base.count) {
                    Text(self.base[$0]).tag($0)
                    }
                    self.userData.saveBase(baseEntry: self.baseEntry)
                }
            }
            .padding()
    }
}

class UserData:  ObservableObject {
    @Published var baseCurr: Int

    func saveBase(baseEntry: Int) -> () {
        
        baseCurr = baseEntry

        let defaults = UserDefaults.standard
        defaults.set(self.baseCurr, forKey: "base")
    }
}

推荐答案

在 body 中，您只能使用视图 - 您不能执​​行以下操作:

In the body you can only use Views - you can't perform operations like:

self.userData.saveBase(baseEntry: self.baseEntry)

您可以使用 onChange 来保存值:

You may use onChange to save the value:

Picker(selection: $baseEntry, label: Text("Select Base >")) {
    ForEach(0 ..< self.base.count) {
        Text(self.base[$0]).tag($0)
    }
    .onChange(of: baseEntry) {
        self.userData.saveBase(baseEntry: $0)
    }
}

---

请注意，您还可以使用 @AppStorage 从 UserDefaults 自动保存/读取:

---

Note that you can also use @AppStorage to automate saving/reading from UserDefaults:

@AppStorage("base") var baseEntry = 0

并以与 @State 变量相同的方式在 Picker 中使用:

and use in the Picker in the same way as a @State variable:

Picker(selection: $baseEntry, label: Text("Select Base >")) {

这篇关于无法将选取器结果保存到 UserDefaults的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！