redux.swift

// Swift 3

protocol ActionType { }

struct InitialAction: ActionType { }

class Store<State> {
    var state: State!
    typealias Reducer = (State?, ActionType) -> State
    final let reducer: Reducer

    init(with reducer: @escaping Reducer) {
        self.reducer = reducer

        dispatch(InitialAction())
    }

    typealias Subscriber = (Store) -> ()
    final var subscribers = [Subscriber]()

    final func dispatch(_ action: ActionType) {
        self.state = reducer(state, action)
        subscribers.forEach {
            $0(self)
        }
    }

    final func subscribe(with subscriber: @escaping Subscriber) {
        subscribers.append(subscriber)
        subscriber(self)
    }
}