ios - SwiftUI Picker 在 Xcode 11 beta 7 中不再工作

Question

我正在使用选择器让用户选择字体类型。该代码曾经可以正常工作，但现在不再正常工作。我认为在更新到 Xcode 11 beta 7 后它可能已停止工作。我可以点击选取器以调出选取器选项列表，但我之前的选择旁边不再显示复选标记，并且点击选项不再做任何事。我做错了什么还是这只是一个测试错误？

设置字体 View :

struct SettingsFont: View {

  @EnvironmentObject var userSettings: UserSettings

  let fontNames = FontName.allCases

  var body: some View {
    Form {
      Section {
        Picker(selection: $userSettings.fontName, label: Text("Font Type")) {
          ForEach(fontNames, id: \.self) { fontName in
            Text(fontName.rawValue).tag(fontName.rawValue)
              .font(FontFactory.noteFont(for: fontName))
          }
        }
      }
    }
    .listStyle(GroupedListStyle())
    .navigationBarTitle(Text("Font"))
  }

}

用户设置:

import Foundation
import Combine

class UserSettings: ObservableObject {

  var objectWillChange = PassthroughSubject<Void, Never>()

  enum StringSettingsKey: String {
    case fontName
  }

  struct Default {
    static let fontName = FontName.sanFrancisco
  }

  @Published var fontName: FontName = Default.fontName {
    willSet { objectWillChange.send() }
    didSet { set(string: fontName.rawValue, for: .fontName) }
  }

  init() {
    setFromUserDefaults(settingsKey: .fontName)
  }

  private func setFromUserDefaults(settingsKey: StringSettingsKey) {
    if let storedString = UserDefaults.standard.string(forKey: settingsKey.rawValue) {
      switch settingsKey {
      case .fontName: fontName = FontName(rawValue: storedString) ?? Default.fontName
      }
      return
    }
  }

  private func set(string: String, for settingsKey: StringSettingsKey) {
    UserDefaults.standard.set(string, forKey: settingsKey.rawValue)
  }

  private func storedString(for settingsKey: StringSettingsKey) -> String? {
    return UserDefaults.standard.string(forKey: settingsKey.rawValue)
  }

}

字体名称:

enum FontName: String, CaseIterable {
  case sanFrancisco = "San Francisco"
  case bitter = "Bitter"
  case helvetica = "Helvetica"
  case georgia = "Georgia"
  case avenir = "Avenir"
  case menlo = "Menlo"
}

Answer 1

您需要将 View 包装在导航 View 中:

struct SettingsFont: View {

    @EnvironmentObject var userSettings: UserSettings

    let fontNames = FontName.allCases

    var body: some View {
        NavigationView {
            Form {
                Section {
                    Picker(selection: $userSettings.fontName, label: Text("Font Type")) {
                        ForEach(fontNames, id: \.self) { fontName in
                            Text(fontName.rawValue).tag(fontName.rawValue)
                                .font(FontFactory.noteFont(for: fontName))
                        }
                    }
                }
            }
        }
        .navigationBarTitle(Text("Font"))
    }

}

需要导航 View 来导航到带有选项的屏幕，然后导航回来。