Capacitor Preferences API Store

capacitor-store.ts

import { get, writable, type Writable } from 'svelte/store';
import { getObject, setObject } from '$lib/capacitor';

export interface CapacitorStore<T> extends Writable<T> {
	loadInitial: () => Promise<boolean>;
}

// Capacitor stores can not have null as a default value because that is what Capacitor returns by default :shrug:
export function createCapacitorStore<T>(key: string, initialValue: T): CapacitorStore<T> {
	// Create a normal Writable store that will mirror our value in the Capacitor store
	const { subscribe, set: originalSet, update: originalUpdate } = writable<T>(initialValue);

	async function loadInitial(): Promise<boolean> {
		console.log('✨ Initializing Capacitor store:', key);
		const nativeValue = await getObject(key);
		if (nativeValue !== null) {
			originalSet(nativeValue);
			return true;
		} else {
			return false; // Keep in mind that loadInitial will be null if there was an error OR the value was not set yet in the native store
		}
	}

	async function set(value: T): Promise<boolean> {
		const ok = await setObject(key, value);
		if (ok) {
			originalSet(value);
			return true;
		} else {
			return false;
		}
	}

	async function update(updater: (value: T) => T): Promise<boolean> {
		const resolvedUpdaterCallback = updater(get({ subscribe })); // Get the latest Writable value
		const ok = await setObject(key, resolvedUpdaterCallback);

		if (ok) {
			originalUpdate(() => resolvedUpdaterCallback);
			return true;
		} else {
			return false;
		}
	}

	return {
		subscribe, // We use the original subscribe function
		set,
		update,
		loadInitial
	};
}

capacitor.ts

import { Preferences } from '@capacitor/preferences';

export const setObject = async (key: string, value: any): Promise<boolean> => {
	try {
		await Preferences.set({
			key,
			value: JSON.stringify(value)
		});
		return true;
	} catch (e) {
		console.error('Failed to setObject', e);
		return false;
	}
};

export const getObject = async (key: string): Promise<any | null> => {
	try {
		const ret = await Preferences.get({ key });

		if (ret?.value) {
			return JSON.parse(ret.value);
		} else {
			return null;
		}
	} catch (e) {
		console.error('Failed to getObject', e);
		return null;
	}
};

export const deleteObject = async (key: string): Promise<boolean> => {
	try {
		await Preferences.remove({ key });
		return true;
	} catch (e) {
		console.error('Failed to deleteObject', e);
		return false;
	}
};