3. Using APIs

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):

This tutorial has an accompanying GitHub repository called carbon-tutorial-angular 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.

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

Install the app’s dependencies:

Then, start the app:

You should see something similar to where the previous step left off. Stop your app with CTRL-C and let’s get everything installed.

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

Install the following

Using the command:

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 we can use it in our app. When your application is being built and developed, our app will parse environmental variables in any environment file and make them available.

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Go ahead and start your app with npm start, or, if your app is running, you’ll need to restart it to get access to this token.

We need to import the environment at the top of every file that we decide to use it in:

Next, make your client by providing a URI for the GitHub GraphQL API as well as an authorization header using the environmental variable you just added to environment.ts.

Add the following import at the top of repo-table.component.ts:

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.

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, we recommend Apollo’s documentation on this topic.

First, we will add a private apollo parameter of type Apollo to the constructor to get access to the Apollo service.

Next, we will fetch the data in ngOnInit(). Add the folowing code right below the model.header declaration:

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

The column will have two values (url and homepageUrl) and will have the structure of an unordered list. If the repository does not have a home page URL, only render the repository link.

Now let’s create a function that transforms row data to our expected header keys. Notice how we’re using our new linkTemplate to generate the value of the links key in each row.

At this point, we should run our query and console.log() the results to verify that the request is working.

If there’s an issue, we’ll render the corresponding error message. We will also check when loading is true, but add the implementation in the following steps.

Finally, if neither of those are true, it means we have our data! One nice advantage of GraphQL is that as long as there are no errors, we can be certain the properties on the data we requested aren’t undefined.

At the end of the watchQuery in ngOnInit():

The page will look the same as we’re still rendering our static example rows, but if you view your browser’s console (e.g. Chrome DevTools), you should see the response from GitHub!

Now that we have that data, let’s populate the data table. Replace console.log(response); with the following that destructures the organization object. Once we have the repositories, we can call our prepareData() to build the data table rows.

Then, in ngOnInit() delete the static rows since we no longer need them.

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 add the Table Skeleton.

To do so, we will need to modify repo-table.component.html and repo-table.component.ts:

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…

Then replace the comment with:

and at the top of the prepareData() function add:

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.

First we will create an array and populate it with 10 rows at a time.

Next, replace the code where we call preapreData() with:

This initializes the page size to 10 as we also specified in our loading skeleton.

Next we will call selectPage(). This will initialize the offset and use prepareData() to only render the subset of rows for the current “page”.

Finally, let’s import the LinkModule and PaginationModule to repositories.module.ts and repo-table.component.spec and add the template for pagination.

Immediately after the ibm-table closing tag (/>), add the ibm-pagination component.

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.

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

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

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

Then, push to your repository:

Finally, visit carbon-tutorial-angular to “Compare & pull request”. In doing so, make sure that you are comparing to angular-step-3 into base: angular-step-3.