Boolean Preference — createBooleanPreference

Use this helper instead of hand-rolled set/toggle pairs. One factory owns the namespaced actions and registers both reducer cases together.

API

Public import: @themislib/themis/utils/store/boolean-preference. createBooleanPreference<S, Field>(options) takes sliceName, field, setActionName, and toggleActionName; Field defaults to the boolean keys of S.

• field must be a string key whose value type is strictly boolean.
• setAction(value: boolean) has tuple payload [value].
• toggleAction() takes no arguments and flips the current value.
• Action types are ${sliceName}/${setActionName} and ${sliceName}/${toggleActionName}.
• register(builder: BooleanPreferenceReducerBuilder<S>) adds both handlers and returns the chainable builder, preserving initialState.
• Handlers update immutably. createReducer shallow-compares their result, so setting an already-equal flag preserves the incoming state reference.

2. Setup — minimum working slice

import { createBooleanPreference } from "@themislib/themis/utils/store/boolean-preference";
import { createReducer } from "@themislib/themis/utils/store/create-reducer";

type SettingsState = { enabled: boolean; label: string };
const initialState: SettingsState = { enabled: false, label: "beta" };

const enabledPreference = createBooleanPreference<SettingsState>({
  sliceName: "settings",
  field: "enabled",
  setActionName: "setEnabled",
  toggleActionName: "toggleEnabled",
});

export const settingsReducer = enabledPreference.register(createReducer(initialState));
export const { setAction: setEnabled, toggleAction: toggleEnabled } = enabledPreference;

Dispatch like any other action:

store.dispatch(setEnabled(true));
store.dispatch(toggleEnabled());

3. Core patterns

3.2 Chaining multiple preferences

Each .register(builder) returns the same builder with two cases added, so you can compose any number of preferences:

import { createBooleanPreference } from "@themislib/themis/utils/store/boolean-preference";
import { createReducer } from "@themislib/themis/utils/store/create-reducer";

type SettingsState = { darkMode: boolean; compactMode: boolean };
const initialState: SettingsState = { darkMode: false, compactMode: false };
const darkMode = createBooleanPreference<SettingsState>({
  sliceName: "settings", field: "darkMode", setActionName: "setDarkMode", toggleActionName: "toggleDarkMode",
});
const compactMode = createBooleanPreference<SettingsState>({
  sliceName: "settings", field: "compactMode", setActionName: "setCompactMode", toggleActionName: "toggleCompactMode",
});

export const settingsReducer = darkMode.register(
  compactMode.register(createReducer(initialState))
);

.register preserves the reducer's initialState field, so stores and tests can access settingsReducer.initialState.

3.3 Persistence saga

Pair the action with an app-local safe-storage helper, following core/local-storage, to persist the flag:

import { call, takeEvery } from "typed-redux-saga";
import { setLocalStorageItem } from "../utils/safe-local-storage-saga";
import { setEnabled, toggleEnabled } from "./settings-actions";
import { selectEnabled } from "./settings-selectors";

const ENABLED_KEY = "settings/enabled";

function* persistEnabled() {
  const enabled = yield* selectEnabled.effect();
  yield* call(setLocalStorageItem, ENABLED_KEY, JSON.stringify(enabled));
}

export function* settingsPersistenceSaga() {
  yield* takeEvery([setEnabled, toggleEnabled], persistEnabled);
}

4. Common Mistakes

• Do not hand-roll a second set/toggle pair; it can drift from the factory's namespacing and handlers. See API.
• Register the preference before giving the reducer to the Store. Creating the actions alone installs no handlers, so dispatch would silently do nothing.
• Do not bypass the boolean-key constraint with as any; the handler would overwrite a non-boolean field with a boolean.
• Test set, toggle, unchanged-field preservation, and same-reference no-op sets through the registered reducer; see core/testing.

5. See also

• core/reducers — createReducer builder and the same-reference on no-op rule.
• core/actions — createAction<[Params]> tuple payloads.
• core/local-storage — persistence saga for preference fields.