当我运行下面的代码并单击某个帐户时，它会显示与该帐户关联的所有日记行。如果我单击添加按钮，它会使用新的日志行更新日志行列表。但只有一次。当我再次单击它时，它会增加余额，但不会更新行列表。如果您单击另一个帐户，然后单击返回，您将看到完整列表。但它只自动更新列表一次？
我尝试account.lines在列表中替换为self.shared.journalLines.filter({$0.accountID == account.id})但我得到了相同的行为。
这是一个错误还是我错过了什么？如果这是一个错误，解决方法是什么？
import SwiftUI
struct ContentView: View {
@EnvironmentObject var shared:SharedObject
var body: some View {
NavigationView {
VStack {
Button(action: {self.shared.test()}) {Text("Add")}
List(self.shared.accounts) { account in
NavigationLink(destination:
List(self.shared.journalLines.filter({$0.accountID == account.id})) { line in
HStack {
Text(line.payee)
Spacer()
Text("$ \(line.amount, specifier: "%.2f")")
}
}.frame(maxWidth: .infinity, maxHeight: .infinity)
) {
HStack {
Text(account.name)
Spacer()
Text("$ \(account.balance, specifier: "%.2f")")
}
}
}
.frame(width: 200)
}
}.frame(maxWidth: .infinity, maxHeight: .infinity)
}
}
struct Account:Identifiable {
@ObservedObject var shared:SharedObject
var id:Int
var name:String
var lines:[JournalLine] {
return self.shared.journalLines.filter({$0.accountID == self.id})
}
var balance:Double {
return self.lines.map({$0.amount}).reduce(0){$0+$1}
}
}
struct JournalLine:Identifiable {
@ObservedObject var shared:SharedObject
let id:UUID = UUID()
var payee:String
var accountID:Int
var amount:Double
}
class SharedObject:ObservableObject {
@Published var accounts:[Account] = []
@Published var journalLines:[JournalLine] = []
init() {
self.accounts.append(Account(shared: self,id: 1, name: "Account#1"))
self.accounts.append(Account(shared: self,id: 2, name: "Account#2"))
self.accounts.append(Account(shared: self,id: 3, name: "Account#3"))
self.journalLines.append(JournalLine(shared: self, payee: "Payee1", accountID: 1, amount: 100))
self.journalLines.append(JournalLine(shared: self, payee: "Payee2", accountID: 1, amount: 200))
self.journalLines.append(JournalLine(shared: self, payee: "Payee3", accountID: 2, amount: 300))
self.journalLines.append(JournalLine(shared: self, payee: "Payee4", accountID: 2, amount: 400))
self.journalLines.append(JournalLine(shared: self, payee: "Payee5", accountID: 3, amount: 500))
self.journalLines.append(JournalLine(shared: self, payee: "Payee6", accountID: 3, amount: 600))
}
func test() {
self.journalLines.append(JournalLine(shared: self, payee: "Payee10", accountID: 1, amount: 100))
self.journalLines.append(JournalLine(shared: self, payee: "Payee10", accountID: 2, amount: 100))
self.journalLines.append(JournalLine(shared: self, payee: "Payee10", accountID: 3, amount: 100))
}
}
编辑：根据评论中的建议修改代码。实施更改后仍然出现相同的错误
import SwiftUI
struct ContentView: View {
@EnvironmentObject var shared:SharedObject
var body: some View {
NavigationView {
VStack {
Button(action: {self.shared.test()}) {Text("Add")}.padding()
List {
ForEach(self.shared.accounts) { account in
NavigationLink(destination:
List {
ForEach(self.shared.journalLines.filter({$0.accountID == account.id})) { line in
HStack {
Text(line.payee)
Spacer()
Text("$ \(line.amount, specifier: "%.2f")")
}
}
}.frame(maxWidth: .infinity, maxHeight: .infinity)
) {
HStack {
Text(account.name)
Spacer()
Text("$ \(self.shared.journalLines.filter({$0.accountID == account.id}).map({$0.amount}).reduce(0){$0+$1}, specifier: "%.2f")")
}
}
}
}
.frame(width: 200)
}
}.frame(maxWidth: .infinity, maxHeight: .infinity)
}
}
class Account:Identifiable {
init(id:Int,name:String) {
self.id=id
self.name=name
}
var id:Int
var name:String
}
class JournalLine:Identifiable {
init(payee:String,accountID:Int,amount:Double) {
self.payee=payee
self.accountID=accountID
self.amount=amount
}
let id:UUID = UUID()
var payee:String
var accountID:Int
var amount:Double
}
class SharedObject:ObservableObject {
@Published var accounts:[Account] = []
@Published var journalLines:[JournalLine] = []
init() {
self.accounts.append(Account(id: 1, name: "Account#1"))
self.accounts.append(Account(id: 2, name: "Account#2"))
self.accounts.append(Account(id: 3, name: "Account#3"))
self.journalLines.append(JournalLine(payee: "Payee1", accountID: 1, amount: 100))
self.journalLines.append(JournalLine(payee: "Payee2", accountID: 1, amount: 200))
self.journalLines.append(JournalLine(payee: "Payee3", accountID: 2, amount: 300))
self.journalLines.append(JournalLine(payee: "Payee4", accountID: 2, amount: 400))
self.journalLines.append(JournalLine(payee: "Payee5", accountID: 3, amount: 500))
self.journalLines.append(JournalLine(payee: "Payee6", accountID: 3, amount: 600))
}
func test() {
self.journalLines.append(JournalLine(payee: "Payee10", accountID: 1, amount: 100))
self.journalLines.append(JournalLine(payee: "Payee10", accountID: 2, amount: 100))
self.journalLines.append(JournalLine(payee: "Payee10", accountID: 3, amount: 100))
}
}
这是我在 SwiftUI 的 List/LazyVStack 中观察到的一个常见问题。
我使用了一个简单的技巧来解决这个问题。将 UniqueID 分配给您想要动态更新的视图。
列表示例：
List(items, id: \.self) {
Text($0.name)
}
.id(UUID())
LazyVStack 的示例：
LazyVStack {
ForEach(items, id: \.self) { item in
Text(item.name)
}
}
.id(UUID())
小智 3
回答
我不知道这是一个错误还是功能，但列表是静态的，这意味着不寻找更新。如果您想跟踪更新，目前常见的解决方法是将 ForEach 放置在 List 中。这样，每次更新@Published对象时，您的视图都会更新。
以下是如何执行列表+ foreach 部分https://www.hackingwithswift.com/quick-start/swiftui/building-a-menu-using-list
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