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Sergey Leschev
Sergey Leschev

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Redux-like state container in SwiftUI. Reducer composition.

Important component of Redux-like state container is Reducer. We can extract and compose it as we do with state struct. It will allow us to respect a Single Responsibility principle and keep our reducers small and clean.

enum AppAction {
    case calendar(action: CalendarAction)
    case trends(action: TrendsAction)
}

func trendsReducer(
    state: inout TrendsState,
    action: TrendsAction
) -> AnyPublisher<TrendsAction, Never> {
    // Implement your state changes here
}

func calendarReducer(
    state: inout CalendarState,
    action: CalendarAction
) -> AnyPublisher<CalendarAction, Never>{
    // Implement your state changes here
}

func appReducer(
    state: inout AppState,
    action: AppAction
) -> AnyPublisher<AppAction, Never> {
    switch action {
    case let .calendar(action):
        return calendarReducer(&state.calendar, action)
            .map(AppAction.calendar)
            .eraseToAnyPublisher()
    case let .trends(action):
        trendsReducer(&state.trends, action)
            .map(AppAction.trends)
            .eraseToAnyPublisher()
    }

    return Empty().eraseToAnyPublisher()
}
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Redux provides a single source of truth, which eliminates tons of bugs produced by multiple states across the app. Best practices. Normalization and composition keep our app state simple and maintainable.


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