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3. Using APIs

This step takes our static components and populates them with data from the GitHub GraphQL API – loading states and all. We’ll be displaying Carbon repository information in a data table.

Preview

The GitHub GraphQL API is very well documented, and even though the focus of this tutorial isn’t learning and using GraphQL, it’s a great opportunity to fetch Carbon-related data for this Carbon tutorial.

To do so, we’ll be using Apollo Client, the front-end component of the Apollo Platform. Apollo provides several open source tools for using GraphQL throughout your application’s stack. Apollo Client is a sophisticated GraphQL client that manages data and state in an application.

A preview of what you will build (see repositories page):

Fork, clone and branch

This tutorial has an accompanying GitHub repository called carbon-tutorial-vue that we’ll use as a starting point for each step. If you haven’t forked and cloned that repository yet, and haven’t added the upstream remote, go ahead and do so by following the step 2 instructions.

Branch

With your repository all set up, let’s check out the branch for this tutorial step’s starting point.

git fetch upstream
git checkout -b vue-step-3 upstream/vue-step-3

Build and start app

Install the app’s dependencies:

yarn

Then, start the app:

yarn serve

You should see something similar to where the previous step left off. Stop your app with 

CTRL-C
and let’s get everything installed.

Install dependencies

We’ll shortcut this using the Vue CLI, if you’d like more information head over to Vue Apollo Installation for details.

Note: If you have not yet installed the Vue CLI, you will need to install the Vue CLI before running the Vue Apollo Installation.

Install the following

  • apollo-boost
    - package containing everything you need to set up Apollo Client
  • graphql
    - parses your GraphQL queries
  • vue-apollo
    - Apollo integration for Vue

Using the command:

vue add apollo

At the following prompts answer ‘No’ to each of the questions.

  • Add example code? No
  • Add a GraphQL API Server? No
  • Configure Apollo Engine? No

Create access token

You’ll need a personal access token from your GitHub account in order to make requests to the GitHub API. Check out this guide to see how to get one.

When you get to the scope/permissions step, you can leave them all unchecked. We don’t need any special permissions, we just need access to the public API.

Once you have your token, we need to put it in a place where 

create-vue-app
can use it. When your application is being built and developed, create-vue-app will parse environmental variables in any file that starts with 
.env
and make them available under 
process.env.MY_VARIABLE
.

One caveat is that we need to start our variables with 

VUE_APP_
. You can read more about environmental variables in create-vue-app’s guide.

Note: If you already have a valid GitHub Personal Access Token, you can use that token here.

Since we don’t want to commit this file to Git, we can put it in 

.env.local
which is in our 
.gitignore
list. Your file should just have a single line like this one, where the 
x
s are replaced with your unique token.

VUE_APP_GITHUB_PERSONAL_ACCESS_TOKEN=xxxxxx

Go ahead and start your app with 

yarn serve
, or, if your app is running, you’ll need to restart it to get access to this token.

Connect to Apollo

The 

vue-apollo
plugin has made a number of changes to our project.

If you open 

src/main.js
you will see that the CLI has updated this file with the following:.

import { createProvider } from 'vue-apollo';


new Vue({
  router,
  apolloProvider: createProvider(),
  render: (h) => h(App),
}).$mount('#app');

This is loading from a file the CLI created for you 

src/vue-apollo.js
which we need to update to target the github api.

Update the following values:

// Use our access token
const AUTH_TOKEN = process.env.VUE_APP_GITHUB_PERSONAL_ACCESS_TOKEN;


// Target github api
const httpEndpoint =
  process.env.VUE_APP_GRAPHQL_HTTP || 'https://api.github.com/graphql';

Update only the 

wsEndpoint
and 
getAuth
properties of the 
defaultOptions
object:

const defaultOptions = {
  // set wsEndpoint to null
  wsEndpoint: process.env.VUE_APP_GRAPHQL_WS,


  // Use the form expected by github for authorisation
  getAuth: (tokenName) => `Bearer ${tokenName}`,
};

Fetch data

Imports

Add the following imports to the top of the script section of 

RepoPage.vue
:

import gql from 'graphql-tag';

Query

Next we’ll assemble our GraphQL query to fetch only the data we need from the GraphQL API. We’ll do this using the 

gql
helper we just imported. The 
gql
helper lets you write GraphQL queries using interpolated strings (backticks) in JavaScript. In addition, we’ll be using the 
Query
component from 
vue-apollo
which gives us some great information about our query’s loading state in addition to the data.

You can use GitHub’s explorer tool to write and test your own queries. Try copying the query below and experiment with changing the properties. You can also click the “Docs” button in the top right of the explorer to view all of the available data and query parameters.

If you’d like some more information regarding writing queries and using the Query component, we recommend Apollo’s documentation on this topic.

Add this after your imports:

const REPO_QUERY = gql`
  query REPO_QUERY {
    # Let's use carbon as our organization
    organization(login: "carbon-design-system") {
      # We'll grab all the repositories in one go. To load more resources
      # continuously, see the advanced topics.
      repositories(first: 75, orderBy: { field: UPDATED_AT, direction: DESC }) {
        totalCount
        nodes {

Next, we need to configure apollo in our component script, adding the following after the data() declaration.

apollo: {
  organization: REPO_QUERY
},

At this point, we should run our query view the raw the results to verify that the request is working.

In RepoPage.vue add the following before the 

RepoTable
tag.

{{ this.organization }}

When the data loads you should see the response rendered on your repository page. If not, check the console to see if there are any errors and fix.

Revert this last change and continue.

This data is not quite in the format our 

RepoTable
component is expecting so we’ll use a computed property to transform it. Computed properties in Vue cache and watch their reactive dependencies for us.

Remove the ‘rows’ constant and its use in the data declaration, and add this computed property.

computed: {
  rows() {
      if (!this.organization) {
      return [];
    } else {
      return this.organization.repositories.nodes.map(row => ({
        ...row,
        key: row.id,
        stars: row.stargazers.totalCount,

At this point you have a working table but the links column clearly isn’t what we want.

Helper component

This column in the data table will be a list of repository and home page links, so let’s create a component called 

LinkList
.

Add the following to create your component:

A template section:

<ul class="link-list">
  <li>
    <cv-link :href="url">GitHub</cv-link>
  </li>


  <li v-if="homepageUrl">
    <span>&nbsp;|&nbsp;</span>
    <cv-link :href="homepageUrl">Homepage</cv-link>
  </li>

A script section:

export default {
  name: 'LinkList',
  props: {
    url: String,
    homepageUrl: String,
  },
};

And a style section:

.link-list {
  display: flex;
}

Now let’s make use of this component in our 

RepoTable
component.

At the top of the script section import the link list component:

import LinkList from './LinkList';

And below the name of the component add:

  components: { LinkList },

Then make use of it in our template replacing:

<cv-data-table-cell
  v-for="(cell, cellIndex) in row.data"
  :key="`${cellIndex}`"
  >{{cell}}</cv-data-table-cell>

with

<cv-data-table-cell v-for="(cell, cellIndex) in row.data" :key="`${cellIndex}`">
  <template v-if="!cell.url">
    {{cell}}
  </template>
  <link-list v-else :url="cell.url" :homepage-url="cell.homepageUrl" />
</cv-data-table-cell>

Here in order to switch between the standard rendering of a data cell we’ve wrapped our standard 

{{cell}}
rendering in a template tag. The template tag is non-rendering so it will disappear, leaving us with the same content as before.

Using the v-if and v-else directives we switch based on the contents of the cell between the standard rendering and the LinkList component.

Checking our output again, you should now see the LinkList component rendering the final column.

Next we’ll update our row description. Update the computed property data() in 

RepoTable.vue
to have the following description:

  description: row.description

Check the output again and you should find the descriptions are updated.

After this many refreshes you may have noticed a slight delay in the data loading. As outlined in the documentation, all components contained under one with an apolloProvider have a 

$apollo
attribute. As we added the 
apolloProvider
to our app when creating the Vue instance it is available to us everywhere.

We can use the property to react to loading state.

First let’s demonstrate that this works.

Pass the loading state into our 

RepoTable
component by updating the template with the following:

<repo-table
  :headers="headers"
  :rows="rows"
  title="Carbon Repositories"
  helperText="A collection of public Carbon repositories."
  :loading="$apollo.loading" />

Next add this property to the 

RepoTable
component:

  props: {
    headers: Array,
    rows: Array,
    title: String,
    helperText: String,
    loading: Boolean,
  },

Making use of the property to display a loading message.

Replace:

<cv-data-table
  :columns="columns"
  :title="title"
  :helper-text="helperText"></cv-data-table>

with:

<div v-if="loading">Loading...</div>
<cv-data-table
  v-else
  :columns="columns"
  :title="title"
  :helper-text="helperText"></cv-data-table>

Here we have made use of the v-if and v-else directives to switch content based on the state of 

$apollo.loading
. If you refresh your app you should see this take effect.

Now that we know this is works let’s try something a bit more sophisticated and replace the div containing our loading message with use of the 

CvDataTableSkeleton
component.

<cv-data-table-skeleton
  v-if="loading"
  :columns="columns"
  :title="title"
  :helper-text="helperText"
  :rows="10"
/>

We need to tell the loading skeleton how many rows to render, so let’s use 10 skeleton rows to prepare for the next enhancement…

Add pagination

Pagination! Instead of rendering every repository, let’s add pagination to the data table to only render 10 at a time. Depending on your specific requirements, you may need to fetch new data each time that you interact with the pagination component, but for simplicity, we’re going to make one request to fetch all data, and then paginate the in-memory row data.

Let’s start by adjusting our 

PageTable
component template to add pagination. If you review the storybook notes you’ll see that pagination is added to the data table by supplying a pagination object and listening for pagination events as follows.

  <cv-data-table
    v-else
    :columns="columns"
    :title="title"
    :helper-text="helperText"
    :pagination="{ numberOfItems: this.totalRows }"
    @pagination="$emit('pagination', $event)"
>

Note: 

:prop
is an abbreviation of 
v-bind:prop
. 
@event
is an abbreviation of 
v-on:event
.

In the pagination event we’ve used $emit and $event to re-raise the pagination event to our 

RepoPage
component so that it can arrange to pass only the rows we want to see to the 
RepoTable
component.

We also need to add the 

totalRows
property used in the data tables pagination property.

totalRows: Number,

Next to our 

RepoPage
component, let’s first update our template by updating our 
RepoTable
use with the following attributes.

:rows="pagedRows"
:totalRows="rows.length"
@pagination="onPagination"

replacing

:rows="rows"

Next in the data property of our component add values for 

pageSize
, 
pageStart
and 
page
into the data method return to support our pagination.

  data() {
    return {
      headers,
      pageSize: 0,
      pageStart: 0,
      page: 0
    };
  },

Note: We could have passed values for 

pageSize
and 
page
into our pagination component if we had a specific page or page size we wanted to start with. Instead we are relying on the pagination component to set some sensible defaults and provide us with the details through an event.

Then before we can see our paginated table we need to add: a 

pagedRows
computed property to select the slice of input rows we are interested in, and a method to handle the pagination event.

  computed: {
    // other computed properties
    // ...
    pagedRows() {
      return this.rows.slice(this.pageStart, this.pageStart + this.pageSize);
    }
  },
  methods: {
    onPagination(val) {

Note: Like the other Carbon Vue components, 

Pagination
component examples can be found in Storybook by browsing the story and knobs.

That does it! Your data table should fetch GitHub data on first render. You can expand each row to see the repository’s description. You can modify the pagination items per page and cycle through pages or jump to a specific page of repositories.

Mystery

Hmmm, there is at least one more issue to resolve. If you expand a row or two to see the repository descriptions you will and then change page. What happens?

Assuming you didn’t catch this earlier you will find that the expanded rows, stay expanded after paging. That is if row two was expanded before pagination it is expanded after.

This is because we chose poor values to use as our row and cell keys as we iterated over them. The result is that Vue sees these items as having the same key and makes the assumption that content but not state has changed.

To fix this add the following to the RepoPage component you should be able to find something better.

  watch: {
    rows() {
      if (this.organization) {
        console.dir(this.organization.repositories.nodes);
      }
    }
  },

Hint: 

id
and 
url
are likely unique properties, you could use either of these to update the prototype. In fact we already pass the id value to RepoTable.

Can you fix it?

Submit pull request

We’re going to submit a pull request to verify completion of this tutorial step.

Continuous integration (CI) check

Run the CI check to make sure we’re all set to submit a pull request.

yarn ci-check

Note: Having issues running the CI check? Step 1 has troubleshooting notes that may help.

Git commit and push

Before we can create a pull request, stage and commit all of your changes:

git add --all && git commit -m "feat(tutorial): complete step 3"

Then, push to your repository:

git push origin vue-step-3

Note: Having issues pushing your changes? Step 1 has troubleshooting notes that may help.

Pull request (PR)

Finally, visit carbon-tutorial-vue to “Compare & pull request”. In doing so, make sure that you are comparing to 

vue-step-3
into 
base: vue-step-3
.

Note: Expect your tutorial step PRs to be reviewed by the Carbon team but not merged. We’ll close your PR so we can keep the repository’s remote branches pristine and ready for the next person!

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