[英]EnvironmentObject in TabView - SwiftUI
在我的应用程序中,我有一个费用清单。 我试图让我的 UserSettings 对象在我的 TabView 中链接的所有视图中共享。
基本上,当 PayScheduleForm 中的 userSettings.date 更改时,我希望 ExpenseList 谓词中的 userSettings.date 的值也发生更改。
我相信这样做的方法是使用 EnvironmentObject。 当我启动我的应用程序时,出现以下错误。 我已经看到了一些与此错误相关的链接,但似乎没有一个可以解决我的问题。
Thread 1: Fatal error: No ObservableObject of type UserSettings found. A View.environmentObject(_:) for UserSettings may be missing as an ancestor of this view.
这是我当前的代码:
SceneDelegate.swift
var window: UIWindow?
var settings = UserSettings()
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
let contentView = MainView().environment(\.managedObjectContext, coreDataStack.viewContext).environmentObject(settings)
if let windowScene = scene as? UIWindowScene {
let window = UIWindow(windowScene: windowScene)
window.rootViewController = UIHostingController(rootView: contentView)
self.window = window
window.makeKeyAndVisible()
}
}
主视图.swift
import SwiftUI
import CoreData
@available(iOS 14.0, *)
struct MainView: View {
@EnvironmentObject var userSettings: UserSettings
@Environment(\.managedObjectContext)
var context: NSManagedObjectContext
var nextPaydate: Date{
return Calendar.current.date(byAdding: .day, value: 14, to: userSettings.date ) ?? Date()
}
var body: some View {
TabView {
DashboardView()
.tabItem {
VStack {
Text("Dashboard")
Image(systemName: "chart.pie")
}
}
.tag(0)
ExpenseList(predicate: NSPredicate(format: "expenseDate >= %@ AND expenseDate < %@", userSettings.date as NSDate, nextPaydate as NSDate), sortDescriptor: NSSortDescriptor(key: "expenseDate", ascending: true))
.tabItem {
VStack {
Text("Expense List")
Image(systemName: "list.dash")
}
}
.tag(1)
SettingsView()
.tabItem {
VStack {
Text("Settings")
Image(systemName: "gearshape")
}
}
.tag(2)
NewDashboard()
.tabItem {
VStack {
Text("TEST")
Image(systemName: "exclamationmark.square")
}
}
.tag(3)
}
.environmentObject(userSettings)
.onAppear(perform: changePayPeriod)
}
@available(iOS 14.0, *)
func changePayPeriod(){
let currentDate = Date()
if currentDate > PayScheduleForm().nextPaydate{
self.userSettings.date = PayScheduleForm().nextPaydate
}
}
}
@available(iOS 14.0, *)
struct MainView_Previews: PreviewProvider {
static var previews: some View {
MainView()
}
}
设置视图.swift
import SwiftUI
import CoreData
struct SettingsView: View {
@State var accounts: String = ""
@Environment(\.managedObjectContext)
var context: NSManagedObjectContext
@EnvironmentObject var userSettings: UserSettings
var logToEdit: Accounts?
var body: some View {
NavigationView{
if #available(iOS 14.0, *) {
List{
NavigationLink(destination: AccountsList()) {
Text("Accounts")
}
NavigationLink(destination: CategoriesList()) {
Text("Categories")
}
NavigationLink(destination: PayScheduleForm()) {
Text("Pay Schedule")
}
}.navigationTitle("Settings")
} else {
// Fallback on earlier versions
}
}
.environmentObject(userSettings)
.onAppear(perform: {
getUserDefaults()
})
}
func getPayDate() -> Date{
var date = Date()
if UserDefaults.standard.object(forKey: "payDate") != nil {
date = UserDefaults.standard.object(forKey: "payDate") as! Date
}
let df = DateFormatter()
df.dateFormat = "MM/dd/yyyy"
print(df.string(from: date))
return date
}
func getUserDefaults(){
var date = Date()
if UserDefaults.standard.object(forKey: "payDate") != nil {
date = UserDefaults.standard.object(forKey: "payDate") as! Date
}
let df = DateFormatter()
df.dateFormat = "MM/dd/yyyy"
print(df.string(from: date))
}
}
struct SettingsView_Previews: PreviewProvider {
static var previews: some View {
SettingsView()
}
}
PayScheduleForm.swift
import SwiftUI
import CoreData
@available(iOS 14.0, *)
struct PayScheduleForm: View {
var frequencies = ["Bi-Weekly"]
@Environment(\.managedObjectContext) var context
@EnvironmentObject var userSettings : UserSettings
var currentPayDate: Date {
let calendar = NSCalendar.current
return calendar.startOfDay(for: userSettings.date) << Error shown here
}
var nextPaydate: Date{
return Calendar.current.date(byAdding: .day, value: 14, to: currentPayDate ) ?? Date()
}
var nextPaydateText: String{
return Utils.dateFormatterMed.string(from: nextPaydate)
}
var prevMonthPayStart: Date{
return Calendar.current.date(byAdding: .month, value: -1, to: currentPayDate ) ?? Date()
}
var prevMonthPayEnd: Date{
return Calendar.current.date(byAdding: .month, value: -1, to: nextPaydate ) ?? Date()
}
var prevMonthPayNextCheck: Date{
return Calendar.current.date(byAdding: .day, value: 14, to: prevMonthPayEnd ) ?? Date()
}
var prevWkPayStart: Date{
return Calendar.current.date(byAdding: .day, value: -7, to: currentPayDate ) ?? Date()
}
var body: some View {
Form{
TextField("Paycheck Amount", text: $userSettings.payAmount)
Picker(selection: $userSettings.frequency, label: Text("Pay Frequency")) {
ForEach(0 ..< frequencies.count) {
Text(self.frequencies[$0]).tag(userSettings.frequency)
}
}
DatePicker(selection: $userSettings.date, displayedComponents: .date) {
Text("Last Payday")
}
}.navigationTitle("Pay Settings")
Text("Next Payday: \(nextPaydateText)")
}
}
//struct PayScheduleForm_Previews: PreviewProvider {
// static var previews: some View {
// PayScheduleForm()
// }
//}
您的MainView
本地属性隐藏了环境对象,因此只需将其删除, userSettings
将作为注入的EnvironmentObject
可用
@available(iOS 14.0, *)
struct MainView: View {
// var userSettings = UserSettings() // << remove !!
@EnvironmentObject var userSettings: UserSettings // << add !!
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