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ios - 实现 UserDefaults 时遇到问题

转载 作者：行者123 更新时间：2023-12-04 14:50:28 26 4
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我以前有编码经验，但我对 Swift 和 iOS 都非常陌生。我正在开发一个供个人使用的应用程序，以将我用来帮助管理 ADHD 的多个不同应用程序的功能合并到一个地方。该应用程序的主视图提供了一种跟踪日常支出的方法。我正在尝试使用 UserDefaults 来存储输入的信息，以便在我重新打开应用程序时它仍然存在。该应用程序运行良好，据我所知，我已经正确编写了数据处理，但它根本不起作用。在过去的几天里，包括在这个网站上，我一直在用头撞墙，所以任何帮助将不胜感激。这是应用程序主视图的代码:

    import SwiftUIFontIcon
import SwiftUI
//import UIKit

struct ContentView: View {
    
    @State public var purchases = [Purchases]()
    
    @State public var prices = [Price]()
    
    @State public var isActive = false
    
    @State public var goTo: String = ""
    
    @State public var purchase: String = ""
    
    @State public var price: String = ""
    
    //    @State public var isActive: Bool = false
    
    init(){
        if let data = UserDefaults.standard.data(forKey: "Purchases"){
            if let decoded = try? JSONDecoder().decode([Purchases].self, from: data){
                self.purchases = decoded
                
            }
            return
        }
        self.purchases = []
        if let data2 = UserDefaults.standard.data(forKey: "Bread"){
            if let decoded2 = try? JSONDecoder().decode([Price].self, from: data2){
                self.prices = decoded2
                
            }
            return
        }
        self.prices = []
        
    }
    
    func addItem(){
        
        saveStuff()
        self.purchases.append(Purchases(name: purchase))
        saveStuff()
        purchase = ""
        
    }
    func addPrice(){
        saveBread()
        self.prices.append(Price(name: price))
        saveBread()
        price = ""
        
    }
    func deleteItem(at offsets: IndexSet){
        purchases.remove(atOffsets: offsets)
    }
    func deletePrice(at offsets: IndexSet){
        prices.remove(atOffsets: offsets)
    }
    func saveStuff(){
        if let encodedData = try? JSONEncoder().encode(purchases){
            UserDefaults.standard.set(encodedData, forKey: "Purchases")
        }
        //    return
    }
    
    func saveBread(){
        if let encodedData = try? JSONEncoder().encode(prices){
            UserDefaults.standard.set(encodedData, forKey: "Bread")
        }
        //    return
    }
    func clearList(){
        self.prices.removeAll()
        self.purchases.removeAll()
    }
    
    var body: some View {
        
        NavigationView{
            ZStack {
                Color.gray
                    .edgesIgnoringSafeArea(/*@START_MENU_TOKEN@*/.all/*@END_MENU_TOKEN@*/)
                VStack {
                    //                    Spacer()
                    //                    HStack {
                    //                        //                                    Spacer()
                    //                        NavigationLink(
                    //                            destination: ToDoList(rootIsActive: self.$isActive),
                    //                            isActive: self.$isActive
                    //
                    //                        ){
                    //                            FontIcon.text(.ionicon(code: .ios_list_box), fontsize: 48, color: .black)
                    //                        }
                    //                        Spacer()
                    //                        NavigationLink(destination: ReminderView()){
                    //                            FontIcon.text(.ionicon(code: .ios_warning), fontsize: 48, color: .black)
                    //                        }
                    //                        //                                            Spacer()
                    //                    }
                    Spacer()
                    VStack{
                        Spacer()
                        HStack {
                            Spacer()
                            HStack {
                                Spacer()
                                TextField("Add an Item", text: $purchase)
                                    .padding(12)
                                    .border(Color.black)
                                Spacer()
                                Spacer()
                                Spacer()
                                TextField("Add a Price", text: $price)
                                    .padding(12)
                                    .border(Color.black)
                                //                                Spacer()
                                
                                FontIcon.button(.ionicon(code: .ios_add_circle), action: {
                                    addItem()
                                    addPrice()
                                    saveStuff()
                                    saveBread()
                                }, padding: 12, fontsize: 45, color: .black)
                            }
                            .opacity(1)
                            .padding(12)
                            //                            .border(Color.black)
                            //                            Spacer()
                        }
                        Spacer()
                        VStack {
                            HStack {
                                Spacer()
                                List{
                                    ForEach(purchases){ purchase in
                                        Text(purchase.name)
                                            .cornerRadius(16)
                                            .padding(10)
                                    }
                                    
                                    .onDelete(perform: deleteItem)
                                    //                                    .listStyle(GroupedListStyle())
                                    
                                }
                                Spacer()
                                List{
                                    ForEach(prices){ price in
                                        Text(price.name)
                                            .cornerRadius(16)
                                            .padding(10)
                                    }
                                    .onDelete(perform: deletePrice)
                                    //                                    .onAppear{UITableView.appearance().separatorColor = .clear}
                                }
                                Spacer()
                                
                            }
                            Spacer()
                            HStack {
                                //                                Spacer()
                                //                                FontIcon.button(.ionicon(code: .ios_save), action: {
                                //                                   saveStuff()
                                //                                    saveBread()
                                //                                }, padding: 12, fontsize: 78, color: .green)
                                Spacer()
                                
                                FontIcon.button(.ionicon(code: .ios_trash),action:{
                                    clearList()
                                }, padding: 12, fontsize: 78, color: .red)
                                Spacer()
                                NavigationLink(destination: ViewLists()){
                                    FontIcon.text(.ionicon(code: .ios_filing), fontsize: 58, color: .black)
                                }
                                Spacer()
                                NavigationLink(destination: ViewTotals()){
                                    FontIcon.text(.ionicon(code: .ios_add), fontsize: 58, color: .black)
                                }
                                Spacer()
                                NavigationLink(destination: IncomeView()){
                                    FontIcon.text(.ionicon(code: .ios_musical_note), fontsize: 58, color: .black)
                                    
                                }
                                Spacer()
                                
                            }
                            //                            Spacer()
                        }
                        Spacer()
                    }
                    Spacer()
                }
                .navigationBarTitle("ADD ToolKit", displayMode: .large)
                Spacer()
                //                    .navigationBarTitle("Ledger", displayMode: .large)
                //                Spacer()
            }
            .toolbar{
                ToolbarItem(placement: .primaryAction){
                    //                                                Spacer()
                    //                                            Spacer()
                    HStack {
                        Spacer()
                        NavigationLink(destination: ReminderView()){
                            FontIcon.text(.ionicon(code: .ios_warning), fontsize: 48, color: .black)
                            
                            //                                            Spacer()
                        }
                    }
                    
                }
                ToolbarItem(placement: .navigationBarLeading){
                    HStack {
                        
                        Spacer()
                        NavigationLink(
                            destination: ToDoList(rootIsActive: self.$isActive),
                            isActive: self.$isActive
                            
                        ){
                            FontIcon.text(.ionicon(code: .ios_list_box), fontsize: 48, color: .black)
                        }
                        
                        
                    }
                    
                }
                
            }
            
            
            
            //
            
            
            
            
            
            
            
        }
        
        .background(
            NavigationLink(destination: Text(self.goTo), isActive: $isActive){
                EmptyView()
            })
    }
}



struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

以及我定义所有数组结构的模型代码:

import Foundation
import SwiftUI

struct Purchases: Identifiable, Codable{
    let id: String
    let name: String
    
    init(id: String = UUID().uuidString, name: String){
        self.id = id
        self.name = name
    }
}

struct Price: Identifiable, Codable{
    let id: String
    let name: String
    
    init(id: String = UUID().uuidString, name: String){
        self.id = id
        self.name = name
    }
}

struct ToDo: Identifiable, Codable{
    let id: String
    let name: String
    
    init(id: String = UUID().uuidString, name: String){
        self.id = id
        self.name = name
    }
}
struct Reminder: Identifiable, Codable{
    let id: String
    let name: String
    
    init(id: String = UUID().uuidString, name: String){
        self.id = id
        self.name = name
    }
}

struct Income: Identifiable, Codable{
    let id: String
    let name: String
    
    init(id: String = UUID().uuidString, name: String){
        self.id = id
        self.name = name
    }
}

提前致谢

最佳答案

将下面的代码添加到你项目的.swift文件中

//Allows all Codable Arrays to be saved using AppStorage
extension Array: RawRepresentable where Element: Codable {
    public init?(rawValue: String) {
        guard let data = rawValue.data(using: .utf8),
              let result = try? JSONDecoder().decode([Element].self, from: data)
        else {
            return nil
        }
        self = result
    }

    public var rawValue: String {
        guard let data = try? JSONEncoder().encode(self),
              let result = String(data: data, encoding: .utf8)
        else {
            return "[]"
        }
        return result
    }
}

然后使用@AppStorage vs @State 来保存你想要保存的数组

@AppStorage("Purchases") var purchases: [Purchases] = []
@AppStorage("Bread") var breadPrices: [Price] = []

您可以像写入常规数组一样写入它们

您不需要saveStuff 或saveBread

以下是您的代码的简化版本。我无法复制你的进行测试。

import SwiftUI

struct CodableUserDefaultView: View {
    
    @AppStorage("Purchases") var purchases: [Purchases] = []
    //@State public var purchases = [Purchases]()
    @AppStorage("Bread") var breadPrices: [Price] = []
    //@State public var breadPrices = [Price]()
    
    @State public var isActive = false
    
    @State public var goTo: String = ""
    
    
    @State public var price: String = ""
    
    func addItem(purchaes: Purchases){
        
        self.purchases.append(purchaes)
        
    }
    func addPrice(price: Price){
        self.breadPrices.append(price)
        
    }
    func deleteItem(at offsets: IndexSet){
        purchases.remove(atOffsets: offsets)
    }
    func deletePrice(at offsets: IndexSet){
        breadPrices.remove(atOffsets: offsets)
    }
    
    func clearList(){
        self.breadPrices.removeAll()
        self.purchases.removeAll()
    }
    
    var body: some View {
        List{
            Section(content: {
                ForEach(breadPrices){ price in
                    HStack{
                        Text(price.name)
                        Spacer()
                        Button("purchase", action: {
                            addItem(purchaes: Purchases(name: price.name))
                        })
                    }
                }.onDelete(perform: deletePrice)
                VStack{
                    Text("Bread")
                    TextField("Bread Price", text: $price, onCommit: {
                        addPrice(price: Price(name: price))
                    })
                }
            }, header: {
                Text("Bread")
            })
            Section(content: {
                ForEach(purchases){ purchase in
                    HStack{
                        Text(purchase.name)
                    }
                }.onDelete(perform: deleteItem)
            }, header: {
                Text("Purchases")
            })
        }
    }
}



struct CodableUserDefaultView_Previews: PreviewProvider {
    static var previews: some View {
        CodableUserDefaultView()
    }
}

但是正如评论中所提到的，这确实不是 UserDefaults 的好用处。它适用于较小的东西。

The defaults system allows an app to customize its behavior to match a user’s preferences. For example, you can allow users to specify their preferred units of measurement or media playback speed. Apps store these preferences by assigning values to a set of parameters in a user’s defaults database.

https://developer.apple.com/documentation/foundation/userdefaults

如果您只使用 iOS 或其他数据库系统(如 Firebase、AWS、Azure 等)，您可能需要研究 Core Data。

关于ios - 实现 UserDefaults 时遇到问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/69148980/

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