redux/arc.js
function themeReducer(state = initialState, action) {

    switch (action.type) {

        case CONSTANTS.theme.setTheme:
            return {
                ...state,
                theme: action.theme,
                navigationOptions: action.navigationOptions,
                contentOffset: action.contentOffset,
            }
        default:
            return state
    }
}
function themeReducer(state = initialState, action) {

    switch (action.type) {

        case CONSTANTS.theme.setTheme:
            return {
                ...state,
                theme: action.theme,
                navigationOptions: action.navigationOptions,
                contentOffset: action.contentOffset,
            }
        default:
            return state
    }
}
reducer