Function stateReducer

Consumes actions and queues changes to a piece state with provided reducers.

It's important to note that if the result of an action does not change the state then nothing is queued to the stream.

See

StatefulSubject:class

Example

---------------{'add author','Jane Austin'}--|

stateReducer({
  __INIT__: () => ({ authors: [] }),
  'add author': (state, author) => ({
    ...state,
    authors: [...state.authors, author]
  })
})

--{authors:[]}--{authors:['Jane Austin']}-----
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Example

// The State will be the type of data you want to manipulate.
interface State {
  authors: string[]
}

// The Actions are a record of "action name" to a parameter.
// If the action doesn't require a parameter, use `void`.
type Actions = {
  'add author': string
  'action that doesnt need a parameter': void
}

const controllable = new ControllableStream<StateReducerInput<Actions>>()

// To get the best out of this API, pass the Actions type and State
// during invocation.
controllable
  .pipeThrough(stateReducer<Actions, State>(
    {
      __INIT__: () => ({ authors: [] }),

      'add author': (state, author) => state.authors.includes(author) ? state : {
         ...state,
         authors: [...state.authors, author],
      },

      'action that doesnt need a parameter': (state) => state
    }
  ))
  .pipeTo(write(console.info))
// { action: '__INIT__', state: { authors: [] } }

controllable.enqueue({ action: 'add author', param: 'Jane Austin' })
// { action: 'add author', param: 'Jane Austin', state: { authors: ['Jane Austin'] } }

controllable.enqueue({ action: 'add author', param: 'Jane Austin' })
// **Nothing will be queued as the state did not change.**
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