Update local school class cache after joining a class

client/src/graphql/gql/mutations/joinClass.gql

@@ -1,5 +1,9 @@
 mutation JoinClass($input: JoinClassInput!) {
   joinClass(input: $input) {
     success
+    schoolClass {
+      id
+      name
+    }
   }
 }

client/src/pages/joinClass.vue

@@ -21,6 +21,7 @@
 
 <script>
   import JOIN_CLASS_MUTATION from '@/graphql/gql/mutations/joinClass.gql';
+  import ME_QUERY from '@/graphql/gql/meQuery.gql';
 
   export default {
     data: () => ({
@@ -40,6 +41,18 @@
             input: {
               code
             }
+          },
+          update(store, {data: {joinClass: {schoolClass}}}) {
+            if (schoolClass) {
+              const data = store.readQuery({query: ME_QUERY});
+              if (data) {
+                data.me.schoolClasses.edges.push({
+                  node: schoolClass,
+                  __typename: 'SchoolClassNode'
+                });
+                store.writeQuery({query: ME_QUERY, data});
+              }
+            }
           }
         }).catch(e => {
           console.debug(e);