swiftui-navigation/Sources/SwiftUINavigation/NavigationLink.swift

import SwiftUI

extension NavigationLink {
  /// Creates a navigation link that presents the destination view when a bound value is non-`nil`.
  ///
  /// This allows you to drive navigation to a destination from an optional value. When the
  /// optional value becomes non-`nil` a binding to an honest value is derived and passed to the
  /// destination. Any edits made to the binding in the destination are automatically reflected
  /// in the parent.
  ///
  /// ```swift
  /// struct ContentView: View {
  ///   @State var postToEdit: Post?
  ///   @State var posts: [Post]
  ///
  ///   var body: some View {
  ///     ForEach(self.posts) { post in
  ///       NavigationLink(unwrapping: self.$postToEdit) { isActive in
  ///         self.postToEdit = isActive ? post : nil
  ///       } destination: { $draft in
  ///         EditPostView(post: $draft)
  ///       } onNavigate:  label: {
  ///         Text(post.title)
  ///       }
  ///     }
  ///   }
  /// }
  ///
  /// struct EditPostView: View {
  ///   @Binding var post: Post
  ///   var body: some View { ... }
  /// }
  /// ```
  ///
  /// - Parameters:
  ///   - value: A binding to an optional source of truth for the destination. When `value` is
  ///     non-`nil`, a non-optional binding to the value is passed to the `destination` closure. The
  ///     destination can use this binding to produce its content and write changes back to the
  ///     source of truth. Upstream changes to `value` will also be instantly reflected in the
  ///     destination. If `value` becomes `nil`, the destination is dismissed.
  ///   - onNavigate: A closure that executes when the link becomes active or inactive with a
  ///     boolean that describes if the link was activated or not. Use this closure to populate the
  ///     source of truth when it is passed a value of `true`. When passed `false`, the system will
  ///     automatically write `nil` to `value`.
  ///   - destination: A view for the navigation link to present.
  ///   - label: A view builder to produce a label describing the `destination` to present.
  @available(iOS, introduced: 13, deprecated: 16)
  @available(macOS, introduced: 10.15, deprecated: 13)
  @available(tvOS, introduced: 13, deprecated: 16)
  @available(watchOS, introduced: 6, deprecated: 9)
  public init<Value, WrappedDestination>(
    unwrapping value: Binding<Value?>,
    onNavigate: @escaping (_ isActive: Bool) -> Void,
    @ViewBuilder destination: @escaping (Binding<Value>) -> WrappedDestination,
    @ViewBuilder label: () -> Label
  ) where Destination == WrappedDestination? {
    self.init(
      destination: Binding(unwrapping: value).map(destination),
      isActive: value.isPresent().didSet(onNavigate),
      label: label
    )
  }

  /// Creates a navigation link that presents the destination view when a bound enum is non-`nil`
  /// and matches a particular case.
  ///
  /// This allows you to drive navigation to a destination from an enum of values. When the
  /// optional value becomes non-`nil` _and_ matches a particular case of the enum, a binding to an
  /// honest value is derived and passed to the destination. Any edits made to the binding in the
  /// destination are automatically reflected in the parent.
  ///
  /// ```swift
  /// struct ContentView: View {
  ///   @State var destination: Destination?
  ///   @State var posts: [Post]
  ///
  ///   enum Destination {
  ///     case edit(Post)
  ///     /* other destinations */
  ///   }
  ///
  ///   var body: some View {
  ///     ForEach(self.posts) { post in
  ///       NavigationLink(unwrapping: self.$destination, case: /Destination.edit) { isActive in
  ///         self.destination = isActive ? .edit(post) : nil
  ///       } destination: { $draft in
  ///         EditPostView(post: $draft)
  ///       } label: {
  ///         Text(post.title)
  ///       }
  ///     }
  ///   }
  /// }
  ///
  /// struct EditPostView: View {
  ///   @Binding var post: Post
  ///   var body: some View { ... }
  /// }
  /// ```
  ///
  /// See `NavigationLink.init(unwrapping:destination:onNavigate:label)` for a version of this
  /// initializer that works with optional state instead of enum state.
  ///
  /// - Parameters:
  ///   - enum: A binding to an optional source of truth for the destination. When `enum` is
  ///     non-`nil`, and `casePath` successfully extracts a value, a non-optional binding to the
  ///     value is passed to the `destination` closure. The destination can use this binding to
  ///     produce its content and write changes back to the source of truth. Upstream changes to
  ///     `enum` will also be instantly reflected in the destination. If `enum` becomes `nil`, the
  ///     destination is dismissed.
  ///   - onNavigate: A closure that executes when the link becomes active or inactive with a
  ///     boolean that describes if the link was activated or not. Use this closure to populate the
  ///     source of truth when it is passed a value of `true`. When passed `false`, the system will
  ///     automatically write `nil` to `enum`.
  ///   - destination: A view for the navigation link to present.
  ///   - label: A view builder to produce a label describing the `destination` to present.
  @available(iOS, introduced: 13, deprecated: 16)
  @available(macOS, introduced: 10.15, deprecated: 13)
  @available(tvOS, introduced: 13, deprecated: 16)
  @available(watchOS, introduced: 6, deprecated: 9)
  public init<Enum, Case, WrappedDestination>(
    unwrapping enum: Binding<Enum?>,
    case casePath: CasePath<Enum, Case>,
    onNavigate: @escaping (Bool) -> Void,
    @ViewBuilder destination: @escaping (Binding<Case>) -> WrappedDestination,
    @ViewBuilder label: () -> Label
  ) where Destination == WrappedDestination? {
    self.init(
      unwrapping: `enum`.case(casePath),
      onNavigate: onNavigate,
      destination: destination,
      label: label
    )
  }
}