Swiftui @状态初始值未在init（）上重置变量_Swiftui

Swiftui @状态初始值未在init（）上重置变量

swiftui

Swiftui @状态初始值未在init（）上重置变量,swiftui,Swiftui,我有一个分段控件，我正在使用它作为我的应用程序工具栏中链接到selectedTab变量的选项卡。切换选项卡时，帐户列表会更改，但不会重置行列表。我尝试在所选的上使用initialValue以确保它重置为0，但这没有影响它。我尝试在init中打印，以确保在init之后selected的值为0。每次都是这样，但仍然没有刷新每个列表的行我错过了什么 import SwiftUI import SQLite3 struct ContentView:View { @EnvironmentOb

我有一个分段控件，我正在使用它作为我的应用程序工具栏中链接到selectedTab变量的选项卡。切换选项卡时，帐户列表会更改，但不会重置行列表。我尝试在所选的上使用initialValue以确保它重置为0，但这没有影响它。我尝试在init中打印，以确保在init之后selected的值为0。每次都是这样，但仍然没有刷新每个列表的行

我错过了什么

import SwiftUI
import SQLite3

struct ContentView:View {

    @EnvironmentObject var shared:SharedObject

    var body: some View {
        VStack {
            if shared.selectedTab == 0 {
                LedgerView(ledger: .Accounts)
            } else if shared.selectedTab == 1 {
                LedgerView(ledger: .Budgets)
            } else if shared.selectedTab == 2 {
                ReportsView()
            }
        }.frame(maxWidth: .infinity, maxHeight: .infinity)
    }

}

struct LedgerView:View {

    @EnvironmentObject var shared:SharedObject

    let ledger:LedgerType
    @State var selected:Int = 0

    init(ledger:LedgerType) {
        self.ledger = ledger
        self._selected = State(initialValue: 0)
    }

    var body:some View {
        HStack {
            VStack(alignment: HorizontalAlignment.leading) {
                ForEach(shared.accounts.filter({$0.ledger == ledger})) { account in
                    Text(account.name)
                        .background(account.id == self.selected ? Color.accentColor : Color.clear)
                        .onTapGesture {self.selected = account.id}
                }
            }
            Divider()
            VStack(alignment: HorizontalAlignment.leading) {
                ForEach(shared.journalLines.filter({$0.accountID == selected})) { line in
                    Text("Line#\(line.id)")
                }
            }
        }
    }

}

struct ReportsView:View {
    var body:some View {
        Text("Under Construction ...")
    }
}

class SharedObject:ObservableObject {

    @Published var accounts:[Account] = []
    @Published var journalLines:[JournalLine] = []
    @Published var selectedTab:Int = 0

    init() {
        loadData()    
    }

}

enum LedgerType:Int {
    case Accounts=0,Budgets=1
    var name:String {
        switch(self) {
        case .Accounts: return "Accounts"
        case .Budgets: return "Budgets"
        }
    }
}
struct Account:Identifiable {
    var id:Int
    var name:String
    var ledger:LedgerType
}
struct Payee:Identifiable {
    var id:Int
    var name:String
}
struct Journal:Identifiable {
    var id:Int
    var date:Date
    var payeeID:Int
    var memo:String?
}
struct JournalLine:Identifiable {
    var id:Int
    var journalID:Int
    var accountID:Int
    var amount:Double
}

编辑节略的演示代码，尝试隔离问题

import SwiftUI

struct ContentView: View {

    @EnvironmentObject var shared:SharedObject

    var body: some View {
        VStack {
            Picker(selection: $shared.selectedTab, label: Text("")) {
                Text("Accounts").tag(0)
                Text("Budgets").tag(1)
            }.pickerStyle(SegmentedPickerStyle())
            Divider()
            if shared.selectedTab == 0 || shared.selectedTab == 1 {
                LedgerView()
            }
            Spacer()
        }
        .padding()
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }

}

struct LedgerView:View {

    @State var selected:Int = 0

    init() {
        self._selected = State(initialValue: 0)
        print("LedgerView.init()")
    }

    var body:some View {
        VStack(alignment: HorizontalAlignment.leading) {
            Text("Selected: \(selected)")
            Picker(selection: $selected, label: Text("")) {
                Text("Account#1").tag(1)
                Text("Account#2").tag(2)
                Text("Account#3").tag(3)
            }
        }
    }

}

class SharedObject: ObservableObject {
    @Published var selectedTab:Int = 0
}

根据你最近的评论，你需要的是@Binding而不是@State。解释：struct LedgerView只是一个单独视图中选择器的摘录。调用LedgerView（）时，不会实例化新对象。它只是在该位置添加选择器视图。因此，当需要在切换选项卡上重置选择器时，需要使用绑定重置选择器。这是工作代码。希望能有帮助

struct ContentView: View {

    @EnvironmentObject var shared:SharedObject
    @State var selected: Int = 0

    var body: some View {
        VStack {
            Picker(selection: $shared.selectedTab, label: Text("")) {
                Text("Accounts").tag(0)
                Text("Budgets").tag(1)
            }.pickerStyle(SegmentedPickerStyle())
            Divider()
            if shared.selectedTab == 0 || shared.selectedTab == 1 {
                LedgerView(selected: $selected)
            }
            Spacer()
        }
        .padding()
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .onReceive(shared.$selectedTab) { newValue in
            self.selected = 0
        }
    }
}

struct LedgerView:View {

    @Binding var selected: Int

    var body:some View {
        VStack(alignment: HorizontalAlignment.leading) {
            Text("Selected: \(selected)")
            Picker(selection: $selected, label: Text("")) {
                Text("Account#1").tag(1)
                Text("Account#2").tag(2)
                Text("Account#3").tag(3)
            }
        }
    }
}

[先前的答案包含替代解决方案]

我已经修改了你的代码使代码行正常工作。我添加了示例数据以使代码正常工作。我怀疑问题是否出在你的数据上。此外，我还修改了enum LedgerType，使其具有可移植性。这是工作代码

我在代码中修改了以下内容：

删除将ledgerType传递给LedgerView，因为真相的来源是

@环境对象变量共享：SharedObject

添加了切换选项卡时默认选择第一个帐户的代码。这将在选项卡之间切换时刷新行。请参阅.onReceive中的代码

希望这有帮助。如果你需要什么，请告诉我

struct ContentView:View {

    @EnvironmentObject var shared: SharedObject

    var body: some View {
        VStack {
            Picker(selection: $shared.selectedTab, label: Text("")) {
                ForEach(0 ..< LedgerType.allCases.count) { index in
                    Text(LedgerType.allCases[index].rawValue).tag(index)
                }
            }
            .pickerStyle(SegmentedPickerStyle())

            if shared.selectedTab == 0 || shared.selectedTab == 1 {
                LedgerView()
            } else if shared.selectedTab == 2 {
                ReportsView()
            }
            Spacer()
        }.frame(maxWidth: .infinity, maxHeight: .infinity)
    }

}

struct LedgerView:View {
    @EnvironmentObject var shared:SharedObject
    @State var selected: Int = 0

    var body:some View {
        HStack {
            VStack(alignment: HorizontalAlignment.leading) {
                ForEach(shared.accounts.filter({ $0.ledger == LedgerType.allCases[shared.selectedTab] })) { account in
                    Text(account.name)
                        .background(account.id == self.selected ? Color.accentColor : Color.clear)
                        .onTapGesture {self.selected = account.id}
                }
            }
            Divider()
            VStack(alignment: HorizontalAlignment.leading) {
                ForEach(shared.journalLines.filter({$0.accountID == selected})) { line in
                    Text("Line#\(line.id)")
                }
            }
        }
        .onReceive(shared.$selectedTab) { newValue in
            if let id = self.shared.getInitialAccountId(tabIndex: newValue) {
                self.selected = id
            }
        }
    }
}

struct ReportsView:View {
    var body:some View {
        Text("Under Construction ...")
    }
}

class SharedObject:ObservableObject {

    @Published var accounts:[Account] = []
    @Published var journalLines:[JournalLine] = []
    @Published var selectedTab:Int = 0

    func getInitialAccountId(tabIndex: Int) -> Int? {
        if tabIndex == 0 {
            return accounts.filter({
                $0.ledger == LedgerType.Accounts
            }).first?.id
        }
        else if tabIndex == 1 {
            return accounts.filter({
                $0.ledger == LedgerType.Budgets
            }).first?.id
        }
        else {
            return accounts.filter({
                $0.ledger == LedgerType.Reports
            }).first?.id
        }
    }

    init() {
        accounts = [
            Account(id: 1, name: "Sales", ledger: .Accounts),
            Account(id: 2, name: "Purchase", ledger: .Accounts),
            Account(id: 3, name: "Forecast", ledger: .Budgets)
        ]
        journalLines = [
            // Line for sales
            JournalLine(id: 1, journalID: 10, accountID: 1, amount: 200),
            JournalLine(id: 2, journalID: 20, accountID: 1, amount: 400),
            // Line for purchase
            JournalLine(id: 3, journalID: 30, accountID: 2, amount: 600),
            JournalLine(id: 4, journalID: 40, accountID: 2, amount: 800)
        ]
    }

}

enum LedgerType: String, CaseIterable {
    case Accounts = "Accounts"
    case Budgets = "Budgets"
    case Reports = "Reports"
}

struct Account:Identifiable {
    var id:Int
    var name:String
    var ledger:LedgerType
}

struct Payee:Identifiable {
    var id:Int
    var name:String
}

struct Journal:Identifiable {
    var id:Int
    var date:Date
    var payeeID:Int
    var memo:String?
}

struct JournalLine:Identifiable {
    var id:Int
    var journalID:Int
    var accountID:Int
    var amount:Double
}

struct ContentView:View{
@环境对象变量共享：SharedObject
var body：一些观点{
VStack{
选择器（选择：$shared.selectedTab，标签：文本（“”））{
ForEach（0..Int{
如果tabIndex==0{
返回帐户.filter({
$0.ledger==LedgerType.Accounts
}).第一个？.身份证
}
如果tabIndex==1，则为else{
返回帐户.filter({
$0.ledger==LedgerType.Budgets
}).第一个？.身份证
}
否则{
返回帐户.filter({
$0.ledger==LedgerType.Reports
}).第一个？.身份证
}
}
init（）{
账户=[
账户（id:1，名称：“销售”，分类账：。账户），
账户（id:2，名称：“采购”，分类账：。账户），
账户（id:3，名称：“预测”，分类账：。预算）
]
日记行=[
//销售线
日记行（id:1，日记id:10，帐户id:1，金额：200），
日记行（id:2，日记id:20，帐户id:1，金额：400），
//购买线
日记行（id:3，日记id:30，帐户id:2，金额：600），
日记行（id:4，日记id:40，accountID:2，金额：800）
]
}
}
枚举分类帐类型：字符串，可大小写{
case Accounts=“Accounts”
案例预算=“预算”
案例报告=“报告”
}
结构帐户：可识别{
变量id:Int
变量名称：String
var分类账：分类账类型
}
结构收款人：可识别{
变量id:Int
变量名称：String
}
结构日志：可识别{
变量id:Int
var日期：日期
变量payeid:Int
var备注：字符串？
}
结构日志行：可识别{
变量id:Int
var journalID:Int
var accountID:Int
风险价值金额：双倍
}

根据您最近的评论，您需要的是@Binding而不是@State。解释：struct LedgerView只是一个单独视图中选择器的摘录。调用LedgerView（）时，不会实例化新对象。它只是在该位置添加选择器视图。因此，当需要在切换选项卡上重置选择器时，需要使用绑定重置选择器。这是工作代码。希望能有帮助

struct ContentView: View {

    @EnvironmentObject var shared:SharedObject
    @State var selected: Int = 0

    var body: some View {
        VStack {
            Picker(selection: $shared.selectedTab, label: Text("")) {
                Text("Accounts").tag(0)
                Text("Budgets").tag(1)
            }.pickerStyle(SegmentedPickerStyle())
            Divider()
            if shared.selectedTab == 0 || shared.selectedTab == 1 {
                LedgerView(selected: $selected)
            }
            Spacer()
        }
        .padding()
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .onReceive(shared.$selectedTab) { newValue in
            self.selected = 0
        }
    }
}

struct LedgerView:View {

    @Binding var selected: Int

    var body:some View {
        VStack(alignment: HorizontalAlignment.leading) {
            Text("Selected: \(selected)")
            Picker(selection: $selected, label: Text("")) {
                Text("Account#1").tag(1)
                Text("Account#2").tag(2)
                Text("Account#3").tag(3)
            }
        }
    }
}

[先前的答案包含替代解决方案]

我已经修改了你的代码使代码行正常工作。我添加了示例数据以使代码正常工作。我怀疑问题是否出在你的数据上。我也