Context

Replicates the benefits of a managed object context in SwiftUI. This comes with support for rolling back to the original state as well as undo and redo support.

Based on IanKeen's Transaction property wrapper.

Usage

The following code is provided in the example app in the Example directory of this repository.

It produces a view that shows an editor to edit the first and last name fields.

Each editor can also provide a child editor that has it's own undo stack. When that editor saves, the change is represented as a single undo step in the parent editor.

struct User: Equatable {
    var firstName: String
    var lastName: String
}

struct ContentView: View {

    @State var user = User(firstName: "", lastName: "")
    @State var showEdit = false

    var body: some View {
        VStack {
            Text("First Name: \(user.firstName)")
            Text("Last Name: \(user.lastName)")
            Button("Edit") { showEdit = true }
        }
        .sheet(isPresented: $showEdit) {
            UserEditor(user: Context($user))
        }
    }
}

struct UserEditor: View {
    @Context var user: User
    @State var showEdit = false

    var body: some View {
        VStack {
            TextField("First Name", text: $user.firstName)
            TextField("Last Name", text: $user.lastName)
            HStack {

                Button(systemImage: "arrow.uturn.left", action: $user.undo)
                    .disabled(!$user.canUndo)

                Button(systemImage: "arrow.uturn.right", action: $user.redo)
                    .disabled(!$user.canRedo)

                Group {
                    Button("Save", action: $user.save)
                    Button("Reset", action: $user.reset)
                    Button("Rollback", action: $user.rollback)
                }
                .disabled(!$user.hasChanges)
            }
            Button("New Editor") { showEdit = true }
        }
        .padding()
        .sheet(isPresented: $showEdit) {
            UserEditor(user: $user.child)
        }
    }
}

extension Button where Label == Image {

    init(systemImage name: String, action: @escaping () -> Void) {
        self.init(action: action) {
            Image(systemName: name)
        }
    }
}