Mutation and update cache
Now let's do the integration part. Open src/components/TodoItem.vue
and add the following code below:
<script>+ import gql from 'graphql-tag';export default {...}</script>
Let's define the graphql mutation to update the completed status of the todo
<script>import gql from 'graphql-tag';+ const TOGGLE_TODO = gql`+ mutation update_todos($id: Int!, $isCompleted: Boolean!) {+ update_todos(where: { id: { _eq: $id } }, _set: { is_completed: $isCompleted }) {+ affected_rows+ }+ }+ `;export default {...}</script>
We need to call this.$apollo.mutate
to make the mutation.
export default {props: ['todos', 'type'],methods: {handleTodoToggle: function (todo) {// update todo data in db here+ this.$apollo.mutate({+ mutation: TOGGLE_TODO,+ variables: {+ id: todo.id,+ isCompleted: !todo.is_completed+ },+ update: (store, { data: { update_todos } }) => {+ if (update_todos.affected_rows) {+ // eslint-disable-next-line+ console.log(update_todos);+ }+ },+ });},
The above code will just make a mutation, updating the todo's is_completed property in the database.
To update the cache, we will be using the update
function again to modify the cache. We need to fetch the current list of todos from the cache before modifying it. So let's import the query.
<script>import gql from 'graphql-tag';+ import { GET_MY_TODOS } from "./TodoPrivateList.vue";const TOGGLE_TODO = gql`mutation update_todos($id: Int!, $isCompleted: Boolean!) {update_todos(where: { id: { _eq: $id } }, _set: { is_completed: $isCompleted }) {affected_rows}}`;
Now let's add the code for update
function.
methods: {handleTodoToggle: function (todo) { // eslint-disable-line// update todo data in db herethis.$apollo.mutate({mutation: TOGGLE_TODO,variables: {id: todo.id,isCompleted: !todo.is_completed},update: (store, { data: { update_todos } }) => {if (update_todos.affected_rows) {- // eslint-disable-next-line- console.log(update_todos);+ if (this.type === "private") {+ // Read the data from our cache for this query.+ const data = store.readQuery({+ query: GET_MY_TODOS,+ });+ const toggledTodo = data.todos.find(t => t.id === todo.id);+ toggledTodo.is_completed = !todo.is_completed;+ store.writeQuery({+ query: GET_MY_TODOS,+ data+ });+ }}},});},
We are fetching the existing todos from the cache using cache.readQuery
and updating the is_completed value for the todo that has been updated.
Finally we are writing the updated todo list to the cache using cache.writeQuery
.
Optimistic response
Now let's remove the input lag by adding optimisticResponse
. This adds a fake result as soon as the network request is made so that the UI can render quickly.
handleTodoToggle: function (todo) { // eslint-disable-line// update todo data in db herethis.$apollo.mutate({mutation: TOGGLE_TODO,variables: {id: todo.id,isCompleted: !todo.is_completed},update: (store, { data: { update_todos } }) => {if (update_todos.affected_rows) {if (this.type === "private") {// Read the data from our cache for this query.const data = store.readQuery({query: GET_MY_TODOS,});const toggledTodo = data.todos.find(t => t.id === todo.id);toggledTodo.is_completed = !todo.is_completed;store.writeQuery({query: GET_MY_TODOS,data});}}},+ optimisticResponse: {+ __typename: 'Mutation',+ update_todos: {+ __typename: 'todos',+ id: todo.id,+ is_completed: !todo.is_completed,+ affected_rows: 1+ },+ }});},
Now the fake result should appear quickly in case the network request takes more time. This should trigger a call to update
function which will update the todo temporarily till the actual response from the server is received.