Last time, I wrote a simple Vue application using dummy data in our components. Today, we’re going to link it to the Apollo GraphQL API that I wrote earlier. As said before, Apollo has both a server-component that can integrate with Express, but also a client component that can integrate with Angular, React but also with Vue.
Adding Apollo to our project
To add Apollo, you can either use the Apollo plugin for Vue CLI (if you’re using v3.x), or you can install the following dependencies:
npm install --save vue-apollo graphql apollo-client apollo-link apollo-link-http apollo-cache-inmemory graphql-tagAfter that, you can create a src/apollo/index.js file and add the following content:
import {HttpLink} from 'apollo-link-http';
import {ApolloClient} from 'apollo-client';
import {InMemoryCache} from 'apollo-cache-inmemory';
import Vue from 'vue';
import VueApollo from 'vue-apollo';
Vue.use(VueApollo);
const httpLink = new HttpLink({
uri: 'http://localhost:3000/graphql',
});
const apolloClient = new ApolloClient({
link: httpLink,
cache: new InMemoryCache(),
connectToDevTools: true
});
export default apolloClient;This will export a “standard” Apollo client over HTTP, which we can now import in the main.js file so that we can use it throughout the application. To do this, you need to create a new provider:
const apolloProvider = new VueApollo({
defaultClient: apolloClient
});To be able to do this, I also had to import both the apolloClient from the src/apollo/index.js location and VueApollo:
import VueApollo from 'vue-apollo';
import apolloClient from './apollo';And finally, you also have to add your provider to your Vue instance:
new Vue({
render: h => h(App),
router,
provide: apolloProvider.provide() // Add this
}).$mount('#app');Using queries
Now that we’ve setup our project, you can start writing queries. The first thing I want to do is to replace the dummy data from the QuestionsPage by an actual GraphQL query.
To do this, I’m going to create a separate file called src/questions/queries.js which will contain all the GraphQL queries related to questions. In this file, I’m going to start by exporting an AllQuestions query:
import gql from 'graphql-tag';
export const AllQuestions = gql`
query AllQuestions($query: Pagination!) {
questionCount
questions(query: $query) {
_id
title
firstPost {
_id
voteCount
}
}
}
`;The gql template literal tag library will parse the query for us, so that it can be used within our components. Before we actually start to use our query we need to remove the dummy data, and just replace it by an empty array:
data () {
return {
questions: []
};
}After that, we can add the query to our component:
import QuestionList from './QuestionList';
import {AllQuestions} from './queries';
export default {
apollo: {
questions: {
query: AllQuestions,
variables () {
return {query: {offset: 0, limit: 10}}
}
},
components: {QuestionList},
data () {
return {
questions: []
};
}
}The way Apollo works is that we define the proper type properties (in this case questions), and Apollo will automatically extract questions from the result and pass it to the component.
Working with parameters
As you can see in the example above, we’ve hardcoded the variables section, but in most cases you probably want to customize this. To do this, let’s create two new properties in our component called offset and questionCount:
data () {
return {
offset: 0,
questions: [],
questionCount: 0
};
}The questionCount property will be provided by our backend, and will contain the amount of questions there are, so we can use some kind of pagination component. That means we need to add a new property to the apollo section:
export default {
apollo: {
questions: {
query: AllQuestions,
variables () {
return {query: {offset: this.offset, limit: 10}}
}
},
questionCount: {
query: AllQuestions,
variables () {
return {query: {offset: this.offset, limit: 10}}
}
}
},
// ...
}As you can see, we’re re-using the AllQuestions query for this new property. Apollo will notice that it’s the same query, and it will be executed only once. I also replaced the hardcoded zero by this.offset, which means that Apollo will automatically update both questions and questionCount as soon as the offset changes.
The next step is to add a pagination component to the QuestionsPage component template:
<at-pagination :total="questionCount" show-total v-on:page-change="updateOffset"></at-pagination>In this case, I’m using the pagination component from AT UI, which requires us to send the total property, and has a page-change event that is triggered as soon as we change the page, and will contain the new page number.
Since we’re using an offset (offset N elements) rather than a page number, I’ll have to convert it within the updateOffset method:
methods: {
updateOffset (pageNumber) {
this.offset = (pageNumber - 1) * 10;
}
}One thing you’ll notice is that Apollo uses its own cache when fetching the same page. If you don’t want to do this, you can change your ApolloClient in src/apollo/index.js:
const apolloClient = new ApolloClient({
link: httpLink,
cache: new InMemoryCache(),
connectToDevTools: true,
defaultOptions: {
watchQuery: {fetchPolicy: 'network-only'},
query: {fetchPolicy: 'network-only'}
}
});Working with mutations
Being able to retrieve a list of questions using GraphQL is nice, but it would also be great if I could create new questions as well. To do this, I wrote a new component and created a saveQuestion() method that will do the actual saving:
export default {
components: {QuestionEditor},
data () {
return {title: '', content: ''};
},
methods: {
saveQuestion (question) {
// TODO
}
}
}Writing mutations with Vue and Apollo is a bit different compared to querying. One similarity though is that we need to define our query first, for example:
export const CreateQuestion = gql`
mutation CreateQuestion($input: QuestionInput!) {
createQuestion(input: $input) {
_id
title
}
}
`;After that, we can use the query by using this.$apollo in our component, for example:
saveQuestion (question) {
const input = {...question};
input.authorId = '5aeb5bd99be6ec471bcdff2f'; // Dummy author ID
this.$apollo.mutate({
mutation: CreateQuestion,
variables: {input}
}).then(() => this.$router.push({name: 'Questions'}));
}Within the mutate() function we can provide both the mutation query and the variables we want to pass. In my case, I named the variable $input in my query, so I defined a variable called input in here as well.
This function returns a promise, which can be used to do something as soon as the request completes. In my case, I’m just redirecting it back to the question listing page because I have no better alternative… yet.
With that, we’ve seen the basics about using Apollo with Vue. As usual, you can find the code on GitHub.