signal gathering reducer

gistfile1.txt

extension Reducer {
    func gatherSignals<GlobalState, GlobalAction, GlobalEnvironment, Signal>(
        signalLocations: [WritableKeyPath<GlobalState, Signal?>],
        target: WritableKeyPath<GlobalState, [Signal]>,
        startAction: GlobalAction
    ) -> Reducer<GlobalState, GlobalAction, GlobalEnvironment> {
        .init { state, action, environment in
            
            let signals = signalLocations.compactMap { state[keyPath: $0] }
            signalLocations.forEach { state[keyPath: $0] = nil}
            state[keyPath: target] += signals
            return !signals.isEmpty ? .init(value: startAction) : .none
        }
    }
}

let gatherToastsAndShow = Reducer<AppState, AppAction, AppEnvironment>.combine(
    // 'gathers' toasts
    Reducer<AppState, AppAction, AppEnvironment>.empty.gatherSignals(
        signalLocations: [\AppState.topLevelToast],
        target: \AppState.toasts.configs,
        startAction: .toast(.trigger)
    ),
    // reads toast configs and asynchronously processes them
    toastReducer.pullback(
        state: \.toasts,
        action: /AppAction.toast,
        environment: { _ in () }
    )
)