Reducer

Extensions on Reducer

Methods

pullback(state:action:)

Transforms a reducer that works on local state, action, and environment into one that works on global state, action and environment when the local environment is a subclass of ComposableEnvironment. It accomplishes this by providing 2 transformations to the method:​

func pullback<GlobalState, GlobalAction, GlobalEnvironment>(
    state toLocalState: WritableKeyPath<GlobalState, State>,
    action toLocalAction: CasePath<GlobalAction, Action>
  ) -> Reducer<GlobalState, GlobalAction, GlobalEnvironment>
  where GlobalEnvironment: ComposableEnvironment 

• A writable key path that can get/set a piece of local state from the global state.

• A case path that can extract/embed a local action into a global action.

Because the environment is ComposableEnvironment, its lifecycle is automatically managed by the library. For more information about this reducer, see the discussion about the equivalent function using unbounded environments in swift-composable-architecture.

Parameters

• toLocalState: A key path that can get/set State inside GlobalState.
• toLocalAction: A case path that can extract/embed Action from GlobalAction.

Returns

A reducer that works on GlobalState, GlobalAction, GlobalEnvironment.

pullback(state:action:breakpointOnNil:_:_:)

Transforms a reducer that works on local state, action, and environment into one that works on global state, action and environmentwhen the local environment is a subclass of ComposableEnvironment.

func pullback<GlobalState, GlobalAction, GlobalEnvironment>(
    state toLocalState: CasePath<GlobalState, State>,
    action toLocalAction: CasePath<GlobalAction, Action>,
    breakpointOnNil: Bool = true,
    _ file: StaticString = #file,
    _ line: UInt = #line
  ) -> Reducer<GlobalState, GlobalAction, GlobalEnvironment>
  where GlobalEnvironment: ComposableEnvironment 

It accomplishes this by providing 2 transformations to the method:

• A case path that can extract/embed a piece of local state from the global state, which is typically an enum.

• A case path that can extract/embed a local action into a global action.

Because the environment is ComposableEnvironment, its lifecycle is automatically managed by the library. For more information about this reducer, see the discussion about the equivalent function using unbounded environments in swift-composable-architecture.

Parameters

• toLocalState: A case path that can extract/embed State from GlobalState.
• toLocalAction: A case path that can extract/embed Action from GlobalAction.

Returns

A reducer that works on GlobalState, GlobalAction, GlobalEnvironment.

forEach(state:action:breakpointOnNil:_:_:)

A version of pullback(state:​action) that transforms a reducer that works on an element into one that works on an identified array of elements, when the local environment is a subclass ofComposableEnvironment.

func forEach<GlobalState, GlobalAction, GlobalEnvironment, ID>(
    state toLocalState: WritableKeyPath<GlobalState, IdentifiedArray<ID, State>>,
    action toLocalAction: CasePath<GlobalAction, (ID, Action)>,
    breakpointOnNil: Bool = true,
    _ file: StaticString = #file,
    _ line: UInt = #line
  ) -> Reducer<GlobalState, GlobalAction, GlobalEnvironment>
  where GlobalEnvironment: ComposableEnvironment 

For more information about this reducer, see the discussion about the equivalent function using unbounded environments in swift-composable-architecture.

Parameters

• toLocalState: A key path that can get/set a collection of State elements inside GlobalState.
• toLocalAction: A case path that can extract/embed (Collection.Index, Action) from GlobalAction.
• breakpointOnNil: Raises SIGTRAP signal when an action is sent to the reducer but the identified array does not contain an element with the action's identifier. This is generally considered a logic error, as a child reducer cannot process a child action for unavailable child state.

Returns

A reducer that works on GlobalState, GlobalAction, GlobalEnvironment.

forEach(state:action:breakpointOnNil:_:_:)

A version of pullback(state:​action:​environment:​) that transforms a reducer that works on an element into one that works on a dictionary of element values, when the local environment is a subclass ofComposableEnvironment.

func forEach<GlobalState, GlobalAction, GlobalEnvironment, Key>(
    state toLocalState: WritableKeyPath<GlobalState, [Key: State]>,
    action toLocalAction: CasePath<GlobalAction, (Key, Action)>,
    breakpointOnNil: Bool = true,
    _ file: StaticString = #file,
    _ line: UInt = #line
  ) -> Reducer<GlobalState, GlobalAction, GlobalEnvironment>
  where GlobalEnvironment: ComposableEnvironment 

For more information about this reducer, see the discussion about the equivalent function using unbounded environments in swift-composable-architecture.

Parameters

• toLocalState: A key path that can get/set a dictionary of State values inside GlobalState.
• toLocalAction: A case path that can extract/embed (Key, Action) from GlobalAction.
• breakpointOnNil: Raises SIGTRAP signal when an action is sent to the reducer but the identified array does not contain an element with the action's identifier. This is generally considered a logic error, as a child reducer cannot process a child action for unavailable child state.

Returns

A reducer that works on GlobalState, GlobalAction, GlobalEnvironment.