swift - 在SwiftUI中如何在XcodePreview中设置editMode的环境变量

Question

给定这样的导航堆栈层次结构，其中将编辑按钮添加到另一个源文件中

struct ContentView : View {
  var body: some View {
    NavigationView {
      EditingView()
    }.navigationBarItems(trailing: EditButton())

  }
}

使用“编辑”按钮的 View 位于代码库的其他位置

struct EditingView : View {

  @State var dataValue: String = "Initial Value"
  @Environment(\.editMode) var editMode

    var body: some View {
      VStack(alignment: .leading) {
        if self.editMode?.value == .inactive {
          Text(dataValue)
        } else {
          TextField(($dataValue))
        }
      }.padding()
        .navigationBarTitle("Lets edit some State")
        .navigationBarItems(trailing: EditButton())
  }
}

我可以在预览中以编程方式设置初始编辑模式吗？有没有一种方法可以使用环境在没有编辑按钮的情况下查看EditingView？片段中显示了一些我可以找到工作的方法，但是我希望我能找到一种方法来通过环境编程设置和初始值。

#if DEBUG
struct EditingView_Previews : PreviewProvider {
  static var previews: some View {
    NavigationView {
      VStack {
        EditingView()

        // I would prefer to use an environment variable.
        // Here is the best thought at some code:
        //
        //   `.environment(\.editMode, .inactive)`
        //
        // the compiler Error returned:
        // Type 'Binding<EditMode>?' has no member 'inactive'
        //
        // which I understand since it is a binding
        // not a direct access to an enum variable.
        // But can I set it somehow or should I let the system
        // handle it entirely?

        // So to get around the issue I have an extra edit button
        EditButton()

      }
    }
  }
  // Or this could work
  //.navigationBarItems(trailing: EditButton())
}
#endif

一个示例项目可以在这里找到:
https://github.com/PaulWoodIII/PreviewEditMode

Answer 1

您可以通过添加到预览提供程序中，将其作为常量传递:

.environment(\.editMode, Binding.constant(EditMode.active))

例如。:

struct EditingView_Previews : PreviewProvider {
  static var previews: some View {
    NavigationView {
      EditingView()
      }
    }
    .environment(\.editMode, Binding.constant(EditMode.active))
  }

}