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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 REST API is very well documented, we’ll use it to fetch Carbon-related data for this Carbon tutorial.

To do so, we’ll be using Octokit Core, a client that makes it easy to interact with GitHub’s APIs.

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

Fork, clone and branch

This tutorial has an accompanying GitHub repository called carbon-tutorial-nextjs 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 1 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 v11-next-step-3 upstream/v11-next-step-3

Build and start app

Install the app’s dependencies and build the app:

yarn && yarn build

Then, start the app:

yarn start

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 need to install 

@octokit/core
, a package that allows us to query GitHub APIs easily. Stop your development server with 
CTRL-C
and install the octokit dependency with:

yarn add @octokit/core@4.2.0

Then, start the app again. If your app’s currently running, you’ll need to restart it.

yarn dev

Fetch data

Imports

We’ll be using React Hooks to call a function to fetch our data when the component renders.

Import React’s useEffect by modifying the 

React
import in 
src/app/repos/page.js
.

import React, { useEffect } from 'react';

Add the following import below the react import in 

RepoPage
:

import { Octokit } from '@octokit/core';

Initializing Octokit client

Directly below all your imports, initialize an octokit client which we’ll use to query our 

RepoTable
data:

const octokitClient = new Octokit({});

API Request

Next, we’ll assemble our GitHub API request to fetch a list of repositories that belong to the 

carbon-design-system
GitHub organization. We’ll do this by using a 
useEffect
hook that will use octokit to query GitHub’s API repositories endpoint.

Let’s declare a 

useEffect
hook immediately below the component definition and above the return. We’ll use this to query GitHub’s API when the component first renders:

function RepoPage() {
  useEffect(() => {
    async function getCarbonRepos() {
      const res = await octokitClient.request('GET /orgs/{org}/repos', {
        org: 'carbon-design-system',
        per_page: 75,
        sort: 'updated',
        direction: 'desc',
      });

At this point, if you navigate to the Repositories page 

/repos
in your running app and view your browser’s console (e.g. Chrome DevTools), you should see the response from GitHub!

Helpers

Our last column in the data table will be a comma-separated list of repository and home page links, so let’s create a component called 

LinkList
.

Import 

Link
at the top of 
/app/repos/page.js
. The imports should look like this.

import { Link, Grid, Column } from '@carbon/react';

Then use 

Link
in this component. It has two props (
url
and 
homepageUrl
) and returns an unordered list. If the repository does not have a home page URL, only render the repository link.

const LinkList = ({ url, homepageUrl }) => (
  <ul style={{ display: 'flex' }}>
    <li>
      <Link href={url}>GitHub</Link>
    </li>
    {homepageUrl && (
      <li>
        <span>&nbsp;|&nbsp;</span>
        <Link href={homepageUrl}>Homepage</Link>

As a final helper, let’s create a function that transforms row data to our expected header keys. Notice how we’re using our new 

LinkList
component to generate the value of the 
links
key in each row.

const getRowItems = (rows) =>
  rows.map((row) => ({
    ...row,
    key: row.id,
    stars: row.stargazers_count,
    issueCount: row.open_issues_count,
    createdAt: new Date(row.created_at).toLocaleDateString(),
    updatedAt: new Date(row.updated_at).toLocaleDateString(),
    links: <LinkList url={row.html_url} homepageUrl={row.homepage} />,

Populate data table

Now that we have our data, let’s dispose of our dummy 

rows
and populate the data table with real data.

First, towards the top of 

RepoPage
delete the 
rows
array because we no longer need the example rows.

Next, let’s add a couple variables that will help us store useful information when fetching the data and keep track of the loading state.

We’ll be using React Hooks again to manage our state.

Import React’s useState by modifying the 

React
import.

import React, { useEffect, useState } from 'react';

Then, inside the 

RepoPage
component:

function RepoPage() {
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState();
  const [rows, setRows] = useState([]);

Now, instead of using 

console.log
to log the github data response, let’s treat the response data by passing it through our 
getRowItems
helper and saving the result in our new 
rows
variable. Replace the 
console.log(res.data);
line inside 
if (res.status === 200)
with:

setRows(getRowItems(res.data));

Let’s also replace our error log line inside the 

else
statement with:

setError('Error obtaining repository data');

To complete our 

getCarbonRepos
function, let’s set the loading state to false right after the 
else
statement:

if (res.status === 200) {
  setRows(getRowItems(res.data));
} else {
  setError('Error obtaining repository data');
}
setLoading(false);

Finally, let’s modify our component’s 

return()
statement to display different information depending on the states of our request: loading, error or complete. Replace the current return statement with:

if (loading) {
  return 'Loading...';
}


if (error) {
  return `Error! ${error}`;
}


// If we're here, we've got our data!

Render repository descriptions

The data table component and its pieces use a common React pattern called render props. This is a really powerful way for libraries to give developers control of rendering and manipulating their data.

Revisiting 

RepoTable.js
, we are already passing in our row objects along with headers for each column. The 
render
prop is being used to tell the data table how to render the headers and rows. That prop takes a function that receives the processed headers and rows as arguments as well as some helper functions for rendering the table.

One common hurdle with the data table is how to access data that might not correspond with a table column but is needed to compute the value of a cell that does. The data table component processes and controls only the row properties which corresponds to headers (columns). Because of this, the 

rows
object you get access to in the render prop function is different than the one you passed in to the 
rows
prop.

We need to modify one aspect of the data table because if you expand a row, it says 

Row description
. We want to update that with the repository description coming from the GitHub API. This is an example of where we need a simple look-up function to find the data we care about - data that does not directly correspond to a column.

To do so, in 

RepoTable.js
, add this look-up function as the first lines inside the 
RepoTable
. This should go immediately before the component’s 
return()
.

const getRowDescription = (rowId) => {
  const row = rows.find(({ id }) => id === rowId);
  return row ? row.description : '';
};

Finally, in 

RepoTable.js
, replace 
<p>Row description</p>
with:

<p>{getRowDescription(row.id)}</p>

Add loading

At this point, the first time that you visit the repositories page, we’re querying the GitHub API and rendering the response through the 

DataTable
component. We could stop here, but there’s more to be done! Let’s replace the 
Loading...
string with the DataTableSkeleton component.

To do so, back to 

RepoPage
, add the 
DataTableSkeleton
import by modifying the existing 
@carbon/react
import.

import { Link, DataTableSkeleton, Grid, Column } from '@carbon/react';

Then replace the 

if (loading) return 'Loading...';
with:

if (loading) {
  return (
    <Grid className="repo-page">
      <Column lg={16} md={8} sm={4} className="repo-page__r1">
        <DataTableSkeleton
          columnCount={headers.length + 1}
          rowCount={10}
          headers={headers}
        />

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.

Initialize the new state variables that we’ll use for pagination as the first lines inside the 

RepoPage
.

function RepoPage() {
  const [firstRowIndex, setFirstRowIndex] = useState(0);
  const [currentPageSize, setCurrentPageSize] = useState(10);
...

This initializes the total number of rows and the index of the first row to 

0
, and the page size to 
10
as we also specified in our loading skeleton.

Then we need to update our 

RepoTable
rows
prop to only render the subset of rows for the current “page”. Update 
<RepoTable headers={headers} rows={rows} />
to:

<RepoTable
  headers={headers}
  rows={rows.slice(firstRowIndex, firstRowIndex + currentPageSize)}
/>

Note: We only pass the rows that we want our table to display. We can do this by slicing the array of rows depending on the first item and the page size.

Finally, let’s add the 

Pagination
to update our state variables and cause the data table to render new rows.

Import 

Pagination
by updating the 
@carbon/react
import.

import {
  Link,
  DataTableSkeleton,
  Pagination,
  Grid,
  Column,
} from '@carbon/react';

Immediately after the 

RepoTable
closing tag (
/>
), add the 
Pagination
component using the state variables that we previously initialized.

<Pagination
  totalItems={rows.length}
  backwardText="Previous page"
  forwardText="Next page"
  pageSize={currentPageSize}
  pageSizes={[5, 10, 15, 25]}
  itemsPerPageText="Items per page"
  onChange={({ page, pageSize }) => {
    if (pageSize !== currentPageSize) {

Note: The 

Pagination
component isn’t inherently connected in any way to the 
DataTable
- we need to tell it what to do when a change occurs using the 
onChange
prop. This includes both page size changes and displaying different rows.

Note: Like the other Carbon React 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.

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, format your code, then stage and commit all of your changes:

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

Then, push to your repository:

git push origin v11-next-step-3

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

Pull request (PR)

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

v11-next-step-3
into 
base: v11-next-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!

Note: If your PR fails the CircleCI test with the error 

Can't make a request in offline mode
, try running the following command: 
rm -rf .yarn-offline-mirror node_modules && yarn cache clean && yarn install
. Add and commit the changes once this completes, and try pushing again.

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