graphql query offline cache

closes #35

client/graphql-client.js

@@ -5,6 +5,7 @@ import { HttpLink } from 'apollo-link-http'
 import { onError } from 'apollo-link-error'
 import { createUploadLink } from 'apollo-upload-client'
 import { BatchHttpLink } from 'apollo-link-batch-http'
+import { persistCache } from 'apollo-cache-persist'
 
 const GRAPHQL_URI = '/graphql'
 
@@ -14,7 +15,7 @@ const defaultOptions = {
     errorPolicy: 'ignore'
   },
   query: {
-    fetchPolicy: 'no-cache', //'network-only'
+    fetchPolicy: 'network-first', //'network-only'
     errorPolicy: 'all'
   },
   mutate: {
@@ -62,7 +63,8 @@ const ERROR_HANDLER = ({ graphQLErrors, networkError }) => {
 }
 
 const cache = new InMemoryCache({
-  addTypename: false
+  addTypename: false,
+  dataIdFromObject: object => object.key
 })
 
 const httpOptions = {
@@ -76,6 +78,15 @@ const httpLink = ApolloLink.split(
   new BatchHttpLink(httpOptions)
 )
 
+const initPersistCache = async () => {
+  persistCache({
+    cache,
+    storage: window.localStorage
+  })
+}
+
+initPersistCache()
+
 export const client = new ApolloClient({
   defaultOptions,
   cache,

package.json

@@ -64,6 +64,7 @@
     "@types/node": "^12.11.2",
     "@webcomponents/webcomponentsjs": "^2.2.7",
     "apollo-cache-inmemory": "^1.6.1",
+    "apollo-cache-persist": "^0.1.1",
     "apollo-client": "^2.6.1",
     "apollo-link-batch-http": "^1.2.13",
     "apollo-link-error": "^1.1.10",