Using the GitHub API in your app

Introduction

This guide will help you build a GitHub App and run it on a server. The app you build will add a label to all new issues opened in the repository where the app is installed.

This project will walk you through the following:

• Programming your app to listen for events
• Using the Octokit.rb library to do REST API operations

Once you've worked through the steps, you'll be ready to develop other kinds of integrations using the full suite of GitHub APIs.

Prerequisites

You may find it helpful to have a basic understanding of the following:

• GitHub Apps
• Webhooks
• The Ruby programming language
• REST APIs
• Sinatra

But you can follow along at any experience level. We'll link out to information you need along the way!

Before you begin, you'll need to do the following:

1. Clone the Using the GitHub API in your app repository.

   $ git clone https://github.com/github-developer/using-the-github-api-in-your-app.git

   Inside the directory, you'll find a template_server.rb file with the template code you'll use in this quickstart and a server.rb file with the completed project code.

2. Follow the steps in the Setting up your development environment quickstart to configure and run the template_server.rb app server. If you've previously completed a GitHub App quickstart other than Setting up your development environment, you should register a new GitHub App and start a new Smee channel to use with this quickstart.

   This quickstart includes the same template_server.rb code as the Setting up your development environment quickstart. Note: As you follow along with the Setting up your development environment quickstart, make sure to use the project files included in the Using the GitHub API in your app repository.

   See the Troubleshooting section if you are running into problems setting up your template GitHub App.

Building the app

Now that you're familiar with the template_server.rb code, you're going to create code that automatically adds the needs-response label to all issues opened in the repository where the app is installed.

The template_server.rb file contains app template code that has not yet been customized. In this file, you'll see some placeholder code for handling webhook events and some other code for initializing an Octokit.rb client.

These are the steps you'll complete to create your first GitHub App:

1. Update app permissions
2. Add event handling
3. Create a new label
4. Add label handling

Step 1. Update app permissions

When you first registered your app, you accepted the default permissions, which means your app doesn't have access to most resources. For this example, your app will need permission to read issues and write labels.

To update your app's permissions:

1. Select your app from the app settings page and click Permissions & Webhooks in the sidebar.
2. In the "Permissions" section, find "Issues," and select Read & Write in the "Access" dropdown next to it. The description says this option grants access to both issues and labels, which is just what you need.
3. In the "Subscribe to events" section, select Issues to subscribe to the event.
4. 单击页面底部的“保存更改”。
5. 如果您已经在您的帐户上安装了应用程序，请检查您的电子邮件并按照链接接受新的权限。 每次更改应用程序的权限或 web 挂钩时，安装应用程序的用户（包括您自己）都需要在更改生效之前接受新权限。 也可以通过导航到安装页面并单击应用旁边的“配置”来接受新权限。 您将在页面顶部看到一个横幅，让您知道应用程序正在请求不同的权限。 单击“Details（详细信息）”，然后单击“Accept new permissions（接受新权限）”。

Great! Your app has permission to do the tasks you want it to do. Now you can add the code to make it work.

Step 2. Add event handling

The first thing your app needs to do is listen for new issues that are opened. Now that you've subscribed to the Issues event, you'll start receiving the issues webhook, which is triggered when certain issue-related actions occur. You can filter this event type for the specific action you want in your code.

GitHub sends webhook payloads as POST requests. Because you forwarded your Smee webhook payloads to http://localhost/event_handler:3000, your server will receive the POST request payloads in the post '/event_handler' route.

An empty post '/event_handler' route is already included in the template_server.rb file, which you downloaded in the prerequisites section. The empty route looks like this:

  post '/event_handler' do

    # # # # # # # # # # # #
    # ADD YOUR CODE HERE  #
    # # # # # # # # # # # #

    200 # success status
  end

Use this route to handle the issues event by adding the following code:

case request.env['HTTP_X_GITHUB_EVENT']
when 'issues'
  if @payload['action'] === 'opened'
    handle_issue_opened_event(@payload)
  end
end

Every event that GitHub sends includes a request header called HTTP_X_GITHUB_EVENT, which indicates the type of event in the POST request. Right now, you're only interested in issues event types. Each event has an additional action field that indicates the type of action that triggered the events. For issues, the action field can be assigned, unassigned, labeled, unlabeled, opened, edited, milestoned, demilestoned, closed, or reopened.

To test your event handler, try adding a temporary helper method. You'll update later when you Add label handling. For now, add the following code inside the helpers do section of the code. You can put the new method above or below any of the other helper methods. Order doesn't matter.

def handle_issue_opened_event(payload)
  logger.debug 'An issue was opened!'
end

This method receives a JSON-formatted event payload as an argument. This means you can parse the payload in the method and drill down to any specific data you need. You may find it helpful to inspect the full payload at some point: try changing logger.debug 'An issue was opened! to logger.debug payload. The payload structure you see should match what's shown in the issues webhook event docs.

Great! It's time to test the changes.

In your browser, visit the repository where you installed your app. Open a new issue in this repository. The issue can say anything you like. It's just for testing.

When you look back at your Terminal, you should see a message in the output that says, An issue was opened! Congrats! You've added an event handler to your app. 💪

Step 3. Create a new label

Okay, your app can tell when issues are opened. Now you want it to add the label needs-response to any newly opened issue in a repository the app is installed in.

Before the label can be added anywhere, you'll need to create the custom label in your repository. You'll only need to do this one time. For the purposes of this guide, create the label manually on GitHub. In your repository, click Issues, then Labels, then click New label. Name the new label needs-response.

Now that the label exists, you can program your app to use the REST API to add the label to any newly opened issue.

Step 4. Add label handling

Congrats—you've made it to the final step: adding label handling to your app. For this task, you'll want to use the Octokit.rb Ruby library.

In the Octokit.rb docs, find the list of label methods. The method you'll want to use is add_labels_to_an_issue.

Back in template_server.rb, find the method you defined previously:

def handle_issue_opened_event(payload)
  logger.debug 'An issue was opened!'
end

The add_labels_to_an_issue docs show you'll need to pass three arguments to this method:

• Repo (string in "owner/name" format)
• Issue number (integer)
• Labels (array)

You can parse the payload to get both the repo and the issue number. Since the label name will always be the same (needs-response), you can pass it as a hardcoded string in the labels array. Putting these pieces together, your updated method might look like this:

# When an issue is opened, add a label
def handle_issue_opened_event(payload)
  repo = payload['repository']['full_name']
  issue_number = payload['issue']['number']
  @installation_client.add_labels_to_an_issue(repo, issue_number, ['needs-response'])
end

Try opening a new issue in your test repository and see what happens! If nothing happens right away, try refreshing.

You won't see much in the Terminal, but you should see that a bot user has added a label to the issue.

If so, congrats! You've successfully built a working app! 🎉

You can see the final code in server.rb in the app template repository.

See "Next steps" for ideas about where you can go from here.

Troubleshooting

Here are a few common problems and some suggested solutions. If you run into any other trouble, you can ask for help or advice in the APIs and Integrations discussions on GitHub Community.

• Q: My server isn't listening to events! The Smee client is running in a Terminal window, and I'm sending events on GitHub.com by opening new issues, but I don't see any output in the Terminal window where I'm running the server.

  A: You may not have the correct Smee domain in your app settings. Visit your app settings page and double-check the fields shown in "Register a new app with GitHub." Make sure the domain in those fields matches the domain you used in your smee -u <unique_channel> command in "Start a new Smee channel."

• Q: My app doesn't work! I opened a new issue, but even after refreshing, no label has been added to it.

  A: Make sure all of the following are true:

  • You installed the app on the repository where you're opening the issue.
  • Your Smee client is running in a Terminal window.
  • Your web server is running with no errors in another Terminal window.
  • Your app has read & write permissions on issues and is subscribed to issue events.
  • You checked your email after updating the permissions and accepted the new permissions.

Conclusion

After walking through this guide, you've learned the basic building blocks for developing GitHub Apps! To review, you:

• Programmed your app to listen for events
• Used the Octokit.rb library to do REST API operations

Next steps

Here are some ideas for what you can do next:

• Rewrite your app using GraphQL!
• Rewrite your app in Node.js using Probot!
• Have the app check whether the needs-response label already exists on the issue, and if not, add it.
• When the bot successfully adds the label, show a message in the Terminal. (Hint: compare the needs-response label ID with the ID of the label in the payload as a condition for your message, so that the message only displays when the relevant label is added and not some other label.)
• Add a landing page to your app and hook up a Sinatra route for it.
• Move your code to a hosted server (like Heroku). Don't forget to update your app settings with the new domain.
• Share your project or get advice in the APIs and Integrations discussions on GitHub Community