Reimplementation of SwiftUI EditMode enum for macOS

EditMode.swift

// Documentation comments are copied from the official documentation for iOS.

import SwiftUI

#if os(macOS)

/// Reimplemenation of [EditMode](https://developer.apple.com/documentation/swiftui/editmode) for macOS.
public enum EditMode {

    /// The user can edit the view content.
    case active

    /// The user can’t edit the view content.
    case inactive

    /// The view is in a temporary edit mode.
    case transient
}

extension EditMode: Equatable {}
extension EditMode: Hashable {}

extension EditMode {

    /// Indicates whether a view is being edited.
    ///
    /// This property returns `true` if the mode is something other than inactive.
    public var isEditing: Bool {
        self != .inactive
    }
}

private struct EditModeEnvironmentKey: EnvironmentKey {
    static var defaultValue: Binding<EditMode>? 
}

extension EnvironmentValues {

    /// An indication of whether the user can edit the contents of a view associated with this environment.
    public var editMode: Binding<EditMode>? {
        get {
            self[EditModeEnvironmentKey.self]
        }
        set {
            self[EditModeEnvironmentKey.self] = newValue
        }
    }
}

#endif

// Below extension also don't exist on iOS, so keep them outside of the compiler directive block.

extension EditMode {

    /// Toggles the edit mode between `.inactive` and `.active`.
    public mutating func toggle() {
        switch self {
        case .inactive: self = .active
        case .active: self = .inactive
        case .transient: break
#if os(iOS)
        @unknown default: break
#endif
        }
    }
}

extension Optional where Wrapped == Binding<EditMode> {

    /// Convenience property so call sites can use a clean `editMode.isEditing` instead of the
    /// ugly boilerplate `editMode?.wrappedValue.isEditing == true`.
    public var isEditing: Bool {
        self?.wrappedValue.isEditing == true
    }
}