🦆 RxDucks

What's RxDucks?

RxDucks is a Redux-like framework working on RxSwift. There are various Redux frameworks, this is a framework specialized for RxSwift.

Redux is one of the modern application architectures. For details, refer to the following links.

Requirements

Swift 5.0
RxSwift 4.4 or later

How to Install

CocoaPods

Add the following to your Podfile:

pod "RxDucks"

Carthage

Add the following to your Cartfile:

github "cats-oss/RxDucks"

How to use RxDucks

The minimum required is State, Action, Reducer and Store.

State

For State, prepare property that application state want. For example, when it want the counter that users can increase or decrease, should create counting property.

It does not have to make immutable necessarily.

struct AppState: State {
    var counter: Int = 0
    var user = UserState()
}

struct UserState: State {
    var loggedIn = false
}

Action

Prepare actions for increase and decrease.

struct IncreaseAction: Action {}
struct DecreaseAction: Action {}
struct LogInAction: Action {}

It does not matter whether it is a struct or not, as long as it complies with the Action protocol.

enum CounterAction: Action {
    case increase, decrease
}

If it does not want to notify state to store, use IgnorableAction.

struct ResetAction: IgnorableAction {}

Reducer

Have to prepare Reducer that complies with the Reducer protocol.

struct AppReducer: Reducer {
    func reduce(_ state: AppState, action: Action) -> AppState {
        var state = state

        switch action {
        case is IncreaseAction:
            state.counter += 1
        case is DecreaseAction:
            state.counter -= 1
        case is ResetAction:
            state.counter = 0
        case is LogInAction:
            state.user.loggedIn = true
        default:
            break
        }

        return state
    }
}

It possible that calls the reducer in main reducer. In that case, it is not necessary to conform to the Reducer protocol.

struct CounterReduder {
    static func reduce(_ state: Int, action: Action) -> Int {
        switch action {
        case is IncreaseAction:
            return state + 1
        case is DecreaseAction:
            return state - 1
        case is ResetAction:
            return 0
        default:
            return state
        }
    }
}

struct UserReduder {
    static func reduce(_ state: UserState, action: Action) -> UserState {
        switch action {
        case is LogInAction:
            return UserState(loggedIn: true)
        default:
            return state
        }
    }
}

struct AppReducer: Reducer {
    func reduce(_ state: AppState, action: Action) -> AppState {
        return AppState(counter: CounterReduder.reduce(state.counter, action: action),
                        user: UserReduder.reduce(state.user, action: action))
    }
}

Store

Initialize with the initial state and the instance of the main Reducer.

let store = Store(reducer: AppReducer(), state: AppState())

It can also make the shared instance.

extension Store where State == AppState {
    static let shared = Store(reducer: AppReducer(), state: AppState())
}

Subscribe to the state

It can subscribe to change the state. state subscribes all change. specifyState subscribes specific state change. Then, when the Store subscribes to state and specifyState, it observes the current state, but when subscribes to newState and specifyNewState, it does not observe the current state.

class ViewController: UIViewController {
    let disposeBag = DisposeBag()
    let store = Store(reducer: AppReducer(), state: AppState())

    @IBOutlet weak var statusLabel: UILabel!
    @IBOutlet weak var counterLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        store.state
            .subscribe(onNext: {
                print($0)
            })
            .disposed(by: disposeBag)

        store.specifyNewState { $0.user.loggedIn }
            .map { $0 ? "Log In" : "Log Out" }
            .bind(to: statusLabel.rx.text)
            .disposed(by: disposeBag)

        store.specifyState { $0.counter }
            .map { "\($0)" }
            .bind(to: counterLabel.rx.text)
            .disposed(by: disposeBag)
    }
}

Dispatch an action

It can dispatch an action to mutate the state.

store.dispatch(IncreaseAction())

Also, it possible to bind using dispatcher.

class ViewController: UIViewController {
    let disposeBag = DisposeBag()
    let store = Store(reducer: AppReducer(), state: AppState())

    @IBOutlet weak var increaseButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        increaseButton.rx.tap
            .map { IncreaseAction() }
            .bind(to: store.dispatcher)
            .disposed(by: disposeBag)
    }
}

Middleware

It is similar to Reducer, but it can not mutate the state. What Middleware can do is to dispatch and change new Actions.

struct LoggingMiddleware: Middleware {
    func on(_ store: Store<AppState>, action: Action, next: @escaping (Action) -> Void) -> Disposable {
        print(action)
        next(action)
        return Disposables.create()
    }
}

The reason for returning Disposable is to facilitate asynchronous processing. It has to execute next closure. So if catch some error, should also execute it.

struct LoginMiddleware: Middleware {
    func on(_ store: Store<AppState>, action: Action, next: @escaping (Action) -> Void) -> Disposable {
        switch action {
        case is LogInAction:
            store.dispatch(LoadingAction())

            let request = URLRequest(url: URL(string: "YOUR_URL")!)
            return URLSession.shared.rx.data(request: request)
                .subscribe(onNext: {
                    next(LoadedAction(data: $0))
                }, onError: {
                    next(LoadErrorAction(error: $0))
                })
        default:
            next(action)
        }

        return Disposables.create()
    }
}

Multiple Middleware can be created. They are executed in the order they were created.

let shared = Store(reducer: AppReducer(), state: AppState(), middlewares: LoggingMiddleware(), LoginMiddleware())

LICENSE

Under the MIT license. See LICENSE file for details.

cats-oss / RxDucks