Support of types keys for storage instance

package/src/MMKV.ts

@@ -9,12 +9,13 @@ import type {
 } from './Types';
 import { addMemoryWarningListener } from './MemoryWarningListener';
 
-const onValueChangedListeners = new Map<string, ((key: string) => void)[]>();
+type ListenerType = (key: string) => void;
+const onValueChangedListeners = new Map<string, ListenerType[]>();
 
 /**
  * A single MMKV instance.
  */
-export class MMKV implements MMKVInterface {
+export class MMKV<K extends string> implements MMKVInterface<K> {
   private nativeInstance: NativeMMKV;
   private functionCache: Partial<NativeMMKV>;
   private id: string;
@@ -65,33 +66,33 @@ export class MMKV implements MMKVInterface {
   get isReadOnly(): boolean {
     return this.nativeInstance.isReadOnly;
   }
-  set(key: string, value: boolean | string | number | ArrayBuffer): void {
+  set(key: K, value: boolean | string | number | ArrayBuffer): void {
     const func = this.getFunctionFromCache('set');
     func(key, value);
 
     this.onValuesChanged([key]);
   }
-  getBoolean(key: string): boolean | undefined {
+  getBoolean(key: K): boolean | undefined {
     const func = this.getFunctionFromCache('getBoolean');
     return func(key);
   }
-  getString(key: string): string | undefined {
+  getString(key: K): string | undefined {
     const func = this.getFunctionFromCache('getString');
     return func(key);
   }
-  getNumber(key: string): number | undefined {
+  getNumber(key: K): number | undefined {
     const func = this.getFunctionFromCache('getNumber');
     return func(key);
   }
-  getBuffer(key: string): ArrayBufferLike | undefined {
+  getBuffer(key: K): ArrayBufferLike | undefined {
     const func = this.getFunctionFromCache('getBuffer');
     return func(key);
   }
-  contains(key: string): boolean {
+  contains(key: K): boolean {
     const func = this.getFunctionFromCache('contains');
     return func(key);
   }
-  delete(key: string): void {
+  delete(key: K): void {
     const func = this.getFunctionFromCache('delete');
     func(key);
 
@@ -127,12 +128,12 @@ export class MMKV implements MMKVInterface {
     };
   }
 
-  addOnValueChangedListener(onValueChanged: (key: string) => void): Listener {
-    this.onValueChangedListeners.push(onValueChanged);
+  addOnValueChangedListener(onValueChanged: (key: K) => void): Listener {
+    this.onValueChangedListeners.push(onValueChanged as ListenerType);
 
     return {
       remove: () => {
-        const index = this.onValueChangedListeners.indexOf(onValueChanged);
+        const index = this.onValueChangedListeners.indexOf(onValueChanged as ListenerType);
         if (index !== -1) {
           this.onValueChangedListeners.splice(index, 1);
         }

package/src/MemoryWarningListener.ts

@@ -2,7 +2,9 @@ import { AppState } from 'react-native';
 import type { NativeEventSubscription } from 'react-native';
 import { MMKVInterface } from './Types';
 
-export function addMemoryWarningListener(mmkv: MMKVInterface): void {
+export function addMemoryWarningListener<K extends string = string>(
+  mmkv: MMKVInterface<K>
+): void {
   if (global.WeakRef != null && global.FinalizationRegistry != null) {
     // 1. Weakify MMKV so we can safely use it inside the memoryWarning event listener
     const weakMmkv = new WeakRef(mmkv);

package/src/Types.ts

@@ -81,45 +81,45 @@ export interface Configuration {
 /**
  * Represents a single MMKV instance.
  */
-export interface NativeMMKV {
+export interface NativeMMKV<K extends string = string> {
   /**
    * Set a value for the given `key`.
    *
    * @throws an Error if the value cannot be set.
    */
-  set: (key: string, value: boolean | string | number | ArrayBuffer) => void;
+  set: (key: K, value: boolean | string | number | ArrayBuffer) => void;
   /**
    * Get the boolean value for the given `key`, or `undefined` if it does not exist.
    *
    * @default undefined
    */
-  getBoolean: (key: string) => boolean | undefined;
+  getBoolean: (key: K) => boolean | undefined;
   /**
    * Get the string value for the given `key`, or `undefined` if it does not exist.
    *
    * @default undefined
    */
-  getString: (key: string) => string | undefined;
+  getString: (key: K) => string | undefined;
   /**
    * Get the number value for the given `key`, or `undefined` if it does not exist.
    *
    * @default undefined
    */
-  getNumber: (key: string) => number | undefined;
+  getNumber: (key: K) => number | undefined;
   /**
    * Get a raw buffer of unsigned 8-bit (0-255) data.
    *
    * @default undefined
    */
-  getBuffer: (key: string) => ArrayBufferLike | undefined;
+  getBuffer: (key: K) => ArrayBufferLike | undefined;
   /**
    * Checks whether the given `key` is being stored in this MMKV instance.
    */
-  contains: (key: string) => boolean;
+  contains: (key: K) => boolean;
   /**
    * Delete the given `key`.
    */
-  delete: (key: string) => void;
+  delete: (key: K) => void;
   /**
    * Get all keys.
    *
@@ -139,7 +139,7 @@ export interface NativeMMKV {
    *
    * @throws an Error if the instance cannot be recrypted.
    */
-  recrypt: (key: string | undefined) => void;
+  recrypt: (key: K | undefined) => void;
   /**
    * Trims the storage space and clears memory cache.
    *
@@ -165,14 +165,12 @@ export interface Listener {
   remove: () => void;
 }
 
-export interface MMKVInterface extends NativeMMKV {
+export interface MMKVInterface<K extends string = string> extends NativeMMKV<K> {
   /**
    * Adds a value changed listener. The Listener will be called whenever any value
    * in this storage instance changes (set or delete).
    *
    * To unsubscribe from value changes, call `remove()` on the Listener.
    */
-  addOnValueChangedListener: (
-    onValueChanged: (key: string) => void
-  ) => Listener;
+  addOnValueChangedListener: (onValueChanged: (key: K) => void) => Listener;
 }