atimca

struct User {
    let id: AnyHashable
}
struct NewsState {
    var user: User
    var step: Step
}
extension NewsState {
    enum Step {
        case initial

atimca

struct AppState {
    var user: User
}
enum AppEvent {
    case newUserWasLoaded(User)
}
extension AppEvent {
    static func reduce(state: AppState, event: AppEvent) -> AppState {
        var state = state
        switch event {

atimca

struct AppState {
    var user: User
    var newsState: NewsState?
}
enum AppEvent {
    case newUserWasLoaded(User)
    case newsEvents(NewsEvent)
}

atimca

extension AppEvent {
    static func reduce(state: AppState, event: AppEvent) -> AppState {
        var state = state
        switch event {
        case .newUserWasLoaded(let user):
            state.user = user
        case .newsEvents(let event):
            switch event {
            case .dataLoaded(let data):
                state.newsState?.step = .loaded(data: data)

atimca

extension AppEvent {
    static func reduce(state: AppState, event: AppEvent) -> AppState {
        var state = state
        switch event {
        case .newUserWasLoaded(let user):
            state.user = user
        case .newsEvents(let event):
            if state.newsState == nil {
                state.newsState = NewsState(user: state.user, step: .initial)
            }

atimca

extension AppEvent {
    static func reduce(state: AppState, event: AppEvent) -> AppState {
        var state = state
        switch event {
        case .newUserWasLoaded(let user):
            state.user = user
        case .newsEvents(let event):
            if state.newsState == nil {
                state.newsState = NewsState(user: state.user, step: .initial)
            }

atimca

typealias Reducer = (AppState, AppEvent) -> AppState

atimca

func combine(_ reducers: Reducer...) -> Reducer

atimca

func combine(_ reducers: Reducer...) -> Reducer {
    return { state, event in
        reducers.reduce(state) { state, reducer in
            reducer(state, event)
        }
    }
}

atimca

let firstReducer: Reducer = { state, event in
    var state = state
    switch event {
    case .newUserWasLoaded(let user):
        state.user = user
    default:
        return state
    }
    return state
}