Seda

Seda is a Redux + Command architecture framework for SwiftUI and UIKit.

Architecture

Seda's architecture is a composite of the Redux and the Command.

In general, Redux's reducer returns only a state. But Seda's reducer returns the state and the 'Command' as follows.

func reducer() -> Reducer<AppState> {
    return { action, state in
        var state = state
        var command = Command.none
        ...
        switch action {
        case Foo.asyncAction:
            command = Command.ofAsyncAction { fullfill in
                asyncFunc { value in fulfill(Foo.updateValue(value)) }
            }
        case Foo.updateValue(let value):
            state.value = value
        ...
        }
        ...
        return (state, command)
    }
}

The Command manages async and side effect tasks. The tasks wrapped by the command don't leak out to reducer that should be a pure function. Because of this, we become able to write async and side effect tasks in a reducer in safety.

Install

Swift Package Manager

On Xcode, select 'File' menu -> 'Swift Packages' -> 'Add Package Dependency...'.

CocoaPods

In Podfile,

pod 'Seda', '~> 0.1'

And execute pod install.

How to use

Essentially, Seda is almost Redux.

Define state

Define Redux's state. State must adopt the StateType protocol.

struct State: StateType {
    var count: Int = 0
}

Define action

Define Redux's action. Action must adopt the ActionType protocol.

enum CountAction: ActionType {
    case step(Step)
    case stepDelayed(Step)
}

Implement reducer

Seda's reducer is different a little from Redux's reducer.

Reducer type must be Reducer<State>.

Reducer is called with action and state. And reducer returns state and command.

typealias CounterReducer = Reducer<State>

func counterReducer() -> CounterReducer {
    return { action, state in
        var state = state
        var command = Command.none

        switch action {
        case CountAction.step(let step):
            state.count += step.count
            state.history.append(step)

        case CountAction.stepDelayed(let step):
            command = .ofAsyncAction { fulfill in
                DispatchQueue.global().asyncAfter(deadline: .now() + .seconds(2)) {
                    fulfill(CountAction.step(step))
                }
            }

        default: ()
        }

        return (state, command)
    }
}

Define view

Define SwiftUI view. View must adopt the StatefulView protocol.

struct CounterView: StatefulView {
    @EnvironmentObject var store: Store<State>

    var body: some View {
        ...
    }
}

Create store and pass the store to the view

let store = Store<State>(reducer: counterReducer(), state: State())
let counterView = CounterView().environmentObject(store)