Ruby implementation of redux store

redux.rb

todos_reducer = -> (state, action) {
  state ||= []

  case action[:type]
  when 'add'
    state.push(action[:todo])
  when 'remove'
    state.remove(action[:todo])
  else
    state
  end
}

counter_reducer = -> (state, action) {
  state ||= 0

  case action[:type]
  when 'increment'
    state += 1
  when 'decrement'
    state -= 1
  else
    state
  end
}

counter_listener = -> () { p 'I am counting numbers' }


class ReduxStore
  def self.combine_reducers(reducers)
    -> (state, action) {
      state ||= {}

      reducers.reduce({}) { | next_state, (key, reducer) |
        next_state[key] = reducer.call(state[key], action)
        next_state
      }
    }
  end

  attr_reader :current_state

  def initialize(reducer)
    @reducer = reducer
    @listeners  = []
    @current_state = nil

    dispatch({})
  end

  def dispatch(action)
    @current_state = @reducer.call(@current_state, action)
    @listeners.each { |l| l.call }
  end

  def subscribe(listener)
    @listeners.push(listener)
    -> { @listeners.delete(listener) }
  end
end


root_reducer = ReduxStore.combine_reducers({ counter: counter_reducer, todos: todos_reducer })

# my_counter_store = ReduxStore.new(counter_reducer)
my_counter_store = ReduxStore.new(root_reducer)

my_counter_store.dispatch({ type: 'increment' })
my_counter_store.dispatch({ type: 'add', todo: 'Buy milk' })
my_counter_store.dispatch({ type: 'add', todo: 'Buy milk again' })
my_counter_store.dispatch({ type: 'increment' })
my_counter_store.dispatch({ type: 'increment' })
my_counter_store.dispatch({ type: 'decrement' })
my_counter_store.dispatch({ type: 'decrement' })
my_counter_store.dispatch({ type: 'increment' })

p my_counter_store.current_state