diff --git a/README.md b/README.md
index c93be35..18c6343 100644
--- a/README.md
+++ b/README.md
@@ -70,17 +70,23 @@ type Mutation {
 You can also purge cache in the resolver:
 
 ```ts
+const schema = makeExecutableSchema({
+  schemaDirectives: {
+    purgeCache: PurgeCacheDirective({ extraNodesPath: '__invalid_nodes__' }),
+  },
+})
+
 const resolvers = {
   Mutation: {
     archiveArticle: (parent, args, context) => {
       // ...
-      article[CACHE_KEYWORD] = [
+      article.__invalid_nodes__ = [
         {
-          id: article.id,
+          id: '2',
           type: 'Article',
         },
         {
-          id: comment.id,
+          id: '3',
           type: 'Comment',
         },
       ]
@@ -90,3 +96,10 @@ const resolvers = {
   },
 }
 ```
+
+### TODOs
+
+- [x] responseCachePlugin
+- [x] @logCache
+- [x] @purgeCache
+- [ ] Unit Test
diff --git a/package-lock.json b/package-lock.json
index c4a475b..3d288aa 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "@matters/apollo-response-cache",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 7a2a0d0..2390b13 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@matters/apollo-response-cache",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "Caching and invalidation mechanisms (plugins, directives) of Apollo GraphQL",
   "author": "Matters <hi@matters.news>",
   "license": "MIT",
diff --git a/src/directives/logCache.ts b/src/directives/logCache.ts
index 9630fe9..65d2579 100644
--- a/src/directives/logCache.ts
+++ b/src/directives/logCache.ts
@@ -5,7 +5,33 @@ import { get } from 'lodash'
 import { toNodeFQCKey } from '../utils'
 
 interface LogCacheDirectiveProps {
-  // Custom function to resolve node type
+  /**
+   * Custom function for resolving type from union and interface, or any other use cases.
+   *
+   * ```
+   * // define
+   * const typeResolver = (type: string, result: any) => {
+   *   if (['Node', 'Response'].indexOf(type) >= 0) {
+   *     return result.__type
+   *   }
+   *   return type
+   * }
+   *
+   * const schema = makeExecutableSchema({
+   *   schemaDirectives: {
+   *     purgeCache: PurgeCacheDirective({ typeResolver }),
+   *   }
+   * })
+   *
+   * type Query {
+   *   node(input: NodeInput!): Node @logCache(type: "Node")
+   * }
+   *
+   * // resolved as `Article`
+   * const nodeResult = { id: '2', __type: 'Article' }
+   *
+   * ```
+   */
   typeResolver?: (type: string, node: any) => string
 }
 
@@ -15,9 +41,9 @@ export const LogCacheDirective = ({
   class BaseLogCacheDirective extends SchemaDirectiveVisitor {
     visitFieldDefinition(field: GraphQLField<any, any>): void {
       const { resolve = defaultFieldResolver } = field
-      const { type, identifier } = this.args
 
-      field.resolve = async function (...args) {
+      field.resolve = async (...args) => {
+        const { type, identifier } = this.args
         const [root, _, { __nodeFQCKeySet, __redis }] = args
         const result = await resolve.apply(this, args)
 
diff --git a/src/directives/purgeCache.ts b/src/directives/purgeCache.ts
index 4e31587..b8b5eb5 100644
--- a/src/directives/purgeCache.ts
+++ b/src/directives/purgeCache.ts
@@ -5,9 +5,38 @@ import { get } from 'lodash'
 import { invalidateFQC, Node } from '../utils'
 
 interface PurgeCacheDirectiveProps {
-  // The path to get extra nodes from result.
+  /**
+   * The path to get extra nodes from result object.
+   *
+   * ```
+   * // define
+   * const schema = makeExecutableSchema({
+   *   schemaDirectives: {
+   *     purgeCache: PurgeCacheDirective({ extraNodesPath: '__invalid_nodes__' }),
+   *   }
+   * })
+   *
+   * type Mutation {
+   *   editArticle(id: ID!): Article! @purgeCache(type: "Article")
+   * }
+   *
+   * // @purgeCache will invalidate three nodes: Article:1, Article:2 and Comment:3.
+   * const editArticleResult = {
+   *   id: '1',
+   *   content: '...',
+   *   __invalid_nodes__: [
+   *     { id: '2', type: 'Article' },
+   *     { id: '3', type: 'Comment' }
+   *   ]
+   * }
+   * ```
+   */
   extraNodesPath?: string
-  // Custom function to resolve node type
+  /**
+   * Custom function for resolving type from union and interface, or any other use cases.
+   *
+   * Same as `@logCache`, see `logCache.ts` for details.
+   **/
   typeResolver?: (type: string, node: any) => string
 }
 
@@ -18,9 +47,9 @@ export const PurgeCacheDirective = ({
   class BasePurgeCacheDirective extends SchemaDirectiveVisitor {
     visitFieldDefinition(field: GraphQLField<any, any>): void {
       const { resolve = defaultFieldResolver } = field
-      const { type, identifier } = this.args
 
-      field.resolve = async function (...args) {
+      field.resolve = async (...args) => {
+        const { type, identifier } = this.args
         const [root, _, { __redis }] = args
         const result = await resolve.apply(this, args)
 
diff --git a/src/index.ts b/src/index.ts
index a101166..2892279 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,11 @@
 import responseCachePlugin from './plugins/responseCachePlugin'
 import { LogCacheDirective } from './directives/logCache'
 import { PurgeCacheDirective } from './directives/purgeCache'
+import { invalidateFQC } from './utils'
 
-export { responseCachePlugin, LogCacheDirective, PurgeCacheDirective }
+export {
+  responseCachePlugin,
+  LogCacheDirective,
+  PurgeCacheDirective,
+  invalidateFQC,
+}