已发布Bool变量自动重置

Question

我有以下简单的SwiftUI视图，其中包含一个组件，该组件包含带有复选框的营销偏好选项列表和更新偏好的按钮：

@StateObject var marketingPreferencesViewModel: MarketingPreferencesViewModel
var body: some View {
VStack {
MarketingPreferencesView(viewModel: .init())
Button {
marketingPreferencesViewModel.marketingUpdateRequested()
} label: {
Text("Update prefs")
}
}
}

市场偏好视图如下：

struct MarketingPreferencesView: View {
@ObservedObject var viewModel: MarketingPreferencesViewModel
var body: some View {
VStack(alignment: .leading) {
marketingPreference(type: .email)
marketingPreference(type: .directMail)
marketingPreference(type: .notification)
marketingPreference(type: .sms)
marketingPreference(type: .telephone)
}
}
func marketingPreference(type: MarketingOptions) -> some View {
HStack {
if viewModel.preferencesAreLoading {
ProgressView()
} else {
Button {
switch type {
case .email:
viewModel.emailMarketingEnabled.toggle()
case .notification:
viewModel.notificationMarketingEnabled.toggle()
case .sms:
viewModel.smsMarketingEnabled.toggle()
case .telephone:
viewModel.telephoneMarketingEnabled.toggle()
case .directMail:
viewModel.directMailMarketingEnabled.toggle()
}

} label: {
switch type {
case .email:
viewModel.emailMarketingEnabled ? Image.General.Checkbox.checked : Image.General.Checkbox.unChecked
// ... remaining switch cases follow same pattern
}
}
}
Text(type.title())
}
.padding(.bottom, Constants.bottomPadding)
}

}

市场偏好视图模型：

class MarketingPreferencesViewModel: ObservableObject {
@Published var emailMarketingEnabled = false {
didSet {
print(emailMarketingEnabled)
}
}
@Published var directMailMarketingEnabled = false
@Published var notificationMarketingEnabled = false
@Published var smsMarketingEnabled = false
@Published var telephoneMarketingEnabled = false

private func updateMarketingPreferences() {
// For now, just printing emailMarketingEnabled value for debugging
print(emailMarketingEnabled)
}

func marketingUpdateRequested() {
self.updateMarketingPreferences()
}  
}
}

因此，用户点击营销偏好按钮，这会在视图模型中切换相应的值。

然而，由于某种原因，当我使用marketingUpdateRequested((方法时，如果我检查emailMarketingEnabled的值，即使我已经切换了它，它也总是错误的。

复制步骤：

• 点击emailMarketingEnabled按钮
• "true"打印在控制台中
• 点击"更新首选项"按钮
• 打印"false">

我已经将didSet放在emailMarketingEnabled属性上，看看它是否在其他地方发生了更改，但它没有。为什么，一旦我设置为true，当我点击按钮时，这是false？

Answer 1

您需要实例化MarketingPreferencesViewModel，然后将其传递给MarketingPreferencesView，类似于下面的示例代码：

// -- here
@StateObject var marketingPreferencesViewModel = MarketingPreferencesViewModel()  
var body: some View {
VStack {
MarketingPreferencesView(viewModel: marketingPreferencesViewModel)  // <-- here
Button {
marketingPreferencesViewModel.marketingUpdateRequested()
} label: {
Text("Update prefs")
}
}
}