Helpers for creating reducers for BindableState

Reducer+BindingHelpers.swift

import ComposableArchitecture
import SwiftUI

extension Reducer {
  /// Returns a reducer that applies ``BindingAction`` mutations to `LocalState` on `State`.
  ///
  /// - Parameters:
  ///   - toLocalState: A key path that can get/set `LocalState` inside `State`.
  ///   - toLocalAction: A case path that can extract/embed `BindingAction` of `LocalState` from `Action`.
  /// - Returns: A reducer that applies ``BindingAction`` mutations to `LocalState` on `State`.
  public static func binding<LocalState>(
    state toLocalState: WritableKeyPath<State, LocalState>,
    action toLocalAction: CasePath<Action, BindingAction<LocalState>>
  ) -> Self {
    let reducer = Reducer<LocalState, BindableActionOf<LocalState>, Void>.empty.binding()
    return Reducer<LocalState, BindingAction<LocalState>, Void> { state, action, _ in
      _ = reducer.run(&state, .binding(action), ())
      return .none
    }
    .pullback(state: toLocalState, action: toLocalAction, environment: { _ in })
  }

  /// Returns a reducer that applies ``BindingAction`` mutations to `LocalState` on `State`before running this
  /// reducer's logic.
  ///
  /// - Parameters:
  ///   - toLocalState: A key path that can get/set `LocalState` inside `State`.
  ///   - toLocalAction: A case path that can extract/embed `BindingAction` of `LocalState` from `Action`.
  /// - Returns: A reducer that applies ``BindingAction`` mutations to `LocalState` on `State`before running this
  /// reducer's logic.
  public func binding<LocalState>(
    state toLocalState: WritableKeyPath<State, LocalState>,
    action toLocalAction: CasePath<Action, BindingAction<LocalState>>
  ) -> Self {
    .binding(state: toLocalState, action: toLocalAction).combined(with: self)
  }

  /// Returns a reducer that applies ``BindingAction`` mutations to `LocalState` on `State`.
  ///
  /// - Parameters:
  ///   - toLocalState: A case path that can extract/embed `LocalState` from `State`.
  ///   - toLocalAction: A case path that can extract/embed `BindingAction` of `LocalState` from `Action`.
  /// - Returns: A reducer that applies ``BindingAction`` mutations to `LocalState` on `State`.
  public static func binding<LocalState>(
    state toLocalState: CasePath<State, LocalState>,
    action toLocalAction: CasePath<Action, BindingAction<LocalState>>
  ) -> Self {
    let reducer = Reducer<LocalState, BindableActionOf<LocalState>, Void>.empty.binding()
    return Reducer<LocalState, BindingAction<LocalState>, Void> { state, action, _ in
      _ = reducer.run(&state, .binding(action), ())
      return .none
    }
    .pullback(state: toLocalState, action: toLocalAction, environment: { _ in })
  }

  /// Returns a reducer that applies ``BindingAction`` mutations to `LocalState` on `State`before running this
  /// reducer's logic.
  ///
  /// - Parameters:
  ///   - toLocalState: A case path that can extract/embed `LocalState` from `State`.
  ///   - toLocalAction: A case path that can extract/embed `BindingAction` of `LocalState` from `Action`.
  /// - Returns: A reducer that applies ``BindingAction`` mutations to `LocalState` on `State`before running this
  /// reducer's logic.
  public func binding<LocalState>(
    state toLocalState: CasePath<State, LocalState>,
    action toLocalAction: CasePath<Action, BindingAction<LocalState>>
  ) -> Self {
    .binding(state: toLocalState, action: toLocalAction).combined(with: self)
  }
}

extension ViewStore {
  /// Returns a binding to the resulting bindable state of a given key path.
  ///
  /// - Parameter keyPath: A key path to a specific bindable state.
  /// - Returns: A new binding.
  public func binding<Value: Equatable>(
    _ keyPath: WritableKeyPath<State, BindableState<Value>>
  ) -> Binding<Value> where Action == BindingAction<State> {
    self.binding(get: { $0[keyPath: keyPath].wrappedValue }, send: { .set(keyPath, $0) })
  }
}

/// Helper for creating a bindable action directly to state
private enum BindableActionOf<State>: BindableAction {
  case binding(BindingAction<State>)
}

~LICENSE

MIT License

Copyright (c) 2022 Pat Brown

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