[Slack API Tutorial] Building a Home for Your Slack App 🏡

Your Slack app's App Home is a focused, 1:1 space in Slack shared between individual users and your app. Within every App Home, users find multiple tabs: About, Messages, and the newly introduced Home tab. The home tab is a dynamic and persistent visual interface allowing users to interact privately with your app. Your app can greet users, showcase customized content, or even be a little playful!

Wait, don’t I already have an App Home?

This new feature may sound familiar to you! There's been an event called app_home_opened for some time, triggered when a user selects an app from the left-hand menu. It's a great opportunity, showcased in this tutorial, to welcome a user with a message with timely information.

With the home tab, your app can go beyond messaging to display more organized, dynamic content with blocks in a persistent location independent of conversation.

App Home tabs

This is what the new surface area looks like for the Google Calendar Slack app:

You can view your daily calendar from the app's Home tab, where you can modify your invitation response or join a conference call on Zoom. In the Message tab is where the app sends you direct messages, for example in Google Calendar, the app notifies you by sending a message 1 minute before a meeting. And in the About tab, you can view information about the app.

Creating an App Home

To demonstrate what you can do with App Home, I am going to walk you through with an app called Stickies, which allows users to store short, private notes within the Home tab.

User Flow

1. A user clicks the name of the app under Apps in the left-hand side menu in Slack client
2. The Home tab should be opened by default
3. The user can add a new note by clicking the button in the pane
4. The user fills out the form in a modal window, then clicks Create
5. The Home pane should be automatically updated with the new note entry

App Flow

1. When a user opens the App Home, the app_home_opened event gets triggered to the app server
2. The app uses the user ID from the event payload to display the initial view with a button with views.publish method
3. When the user clicks the “Add a Stickie” button, an interaction gets triggered
4. App opens a modal with form inputs using the views.open method
5. Once the user submits the form, another interaction is triggered with a type of view_submission
6. Update the App Home using views.publish method

Now, let’s create the Stickies app for your workspace. The source code of the app is on Glitch, where you can "remix" and run without deploying code!

🎏🥫 Source code on Glitch

🎏🍴 Remix (fork) the Glitch repo

Setting up your app

First of all, you need to set up your app on Slack. Go to Slack App Management to create an app.

Next, go to Features > Bot User to enable Bot User. You can change the default bot name as you want.

Then, go to Features > OAuth & Permissions to specify the Bot Token Scopes. Select chat.write. (Technically, this sample app does not send any messages, but just follow this instruction for now. To learn more about this new more granular bot permission model, read Installing with OAuth 2.0, Version 2!)

Now, go to Features > App Home (See Step 1 in the screenshot below). As of the time this tutorial is published in November 2019, this feature is still in beta, so click “Sign up” then read and consent to the agreement to use the feature (See Step 1 in the screenshot below).

Once you signed up, the Home tab and the Message Tab should be checked by default, although, for this tutorial, Message Tab is optional.

Next, go to Features > Event Subscription to enable events (See Step 1 in the screenshot below). Then enter your Request URL (Step 2). If you remixed the example Glitch code, your Request URL should be https://_your-project_.glitch.me/slack/events. (Glitch generates a project name when you create a project. So you probably have a project name composed of two random words, such as fluffy-umbrella. You can customize the project name as I did. If your running on your own server, prepend the URL to /slack/events.)

Then, scroll down to Subscribe to bot events to add app_home_opened event (Step 3). Then save (Step 4).

Similarly, you will need to go to Features > Interactivity & Actions to tell Slack where to send interactive payloads Use your Request URL, https://_your-project_.glitch.me/slack/actions then save.

Let’s install the app once. Go to Install App and click to install the app to your workspace and follow the screen. Once the installation process with OAuth is finished, you should now have your OAuth access tokens on the screen.

Now, get ready with your Glitch project window in your browser, or IDE. This is where your environmental variables are stored. Copy the bot token, which begins with xoxb, and paste it into your Glitch project's .env file.

Also in the Slack app config page, get your Signing Secret key at Settings > Basic information, then copy and paste it to the .env too.

Displaying App Home

Setting up your Express server

In this tutorial, I am using Node.js with Express as the web server. All API calls are done with straightforward HTTP requests and responses, so hopefully, the code is readily comprehensible for any language you use.

⚡️ If you prefer developing with Bolt framework, the source code is also available. But the instruction here is using the “vanilla” code!

In your Node.js code, include dependencies and spin up your Express server. You'll need to evaluate the raw request payload to verify the signing secret from Slack. Lines 31-38 in index.js and lines 143-145 show how to run a server with Express, and demonstrate checking the HTTP headers to verify request signature. (For more details about using Signing Secret with Express and Body Parser in Node.js, please read the Verifying the Requests section in a previous tutorial).

Triggering app_home_opened event

Next, use an HTTP POST method route to create an endpoint to receive the event payload. This is where Slack API server sends you a JSON payload when an event is fired. Once you receive the data, check if the event type is app_home_opened, then prepare to display the App Home view.

Here is the simplified code snippet (To see the full code, see the lines 45 - 70 in index.js):

app.post('/slack/events', async(req, res) => {
  const {type, user, channel, tab, text, subtype} = req.body.event;

  if(type === 'app_home_opened') {
    displayHome(user);
  }
}

Now, let’s display a rich content in App Home view with rich message layout, Block Kit:

const displayHome = async(user, data) => {

  const args = {
    token: process.env.SLACK_BOT_TOKEN,
    user_id: user,
    view: await updateView(user)
  };
  const result = await axios.post('/views.publish', qs.stringify(args));
};

To display content in the App Home, call view.publish method. In this example, I am using the axios module to handle the API calls via HTTP POST.

Constructing the View with Block Kit

In this code example, I am calling another function to create JSON to construct the view to be displayed. This function can be reused when you update the view when new content is added later.

This code snippet shows how to build and display the initial view:

const updateView = async(user) => {
    let blocks = [ 
    {
      // Section with text and a button
      type: "section",
      text: {
        type: "mrkdwn",
        text: "*Welcome!* \nThis is a home for Stickers app. You can add small notes here!"
      },
      accessory: {
        type: "button",
        action_id: "add_note", 
        text: {
          type: "plain_text",
          text: "Add a Stickie"
        }
      }
    },
    // Horizontal divider line 
    {
      type: "divider"
    }
  ];

  let view = {
    type: 'home',
    title: {
      type: 'plain_text',
      text: 'Keep notes!'
    },
    blocks: blocks
  }

  return JSON.stringify(view);
};

The blocks array definied in the code snippet above is prototyped with Block Kit Builder.

In the actual source code, the function takes dynamic content where it takes additional content form the interactive button and modal. I’ll explain the part in the later section.

Triggering a button click from a user

When a user clicks the button, a modal pops open.

Notice the action_id is specified in the message building block. Use the identifier to grab the data we need. Once, a user clicks the button, the API server sends your Request URL a payload of the user action, where it contains trigger_id. You need this to open a modal.

app.post('/slack/actions', async(req, res) => {
  const { token, trigger_id, user, actions, type } = JSON.parse(req.body.payload);
  if(actions && actions[0].action_id.match(/add_/)) {
    openModal(trigger_id);
  } 
});

Opening a modal dialog

This is how you create form elements (input box and a drop-down menu with a submit button) in a modal view. For this exercise, let’s just make the form simple with a multi-line text input and pick a color.

To open the modal, call views.open method:

const openModal = async(trigger_id) => {

  const modal = {
    type: 'modal',
    title: {
      type: 'plain_text',
      text: 'Create a stickie note'
    },
    submit: {
      type: 'plain_text',
      text: 'Create'
    },
    blocks: [
      // Text input
      {
        "type": "input",
        "block_id": "note01",
        "label": {
          "type": "plain_text",
          "text": "Note"
        },
        "element": {
          "action_id": "content",
          "type": "plain_text_input",
          "placeholder": {
            "type": "plain_text",
            "text": "Take a note... "
          },
          "multiline": true
        }
      },

      // Drop-down menu      
      {
        "type": "input",
        "block_id": "note02",
        "label": {
          "type": "plain_text",
          "text": "Color",
        },
        "element": {
          "type": "static_select",
          "action_id": "color",
          "options": [
            {
              "text": {
                "type": "plain_text",
                "text": "yellow"
              },
              "value": "yellow"
            },
            {
              "text": {
                "type": "plain_text",
                "text": "blue"
              },
              "value": "blue"
            }
          ]
        }
      }
    ]
  };

  const args = {
    token: process.env.SLACK_BOT_TOKEN,
    trigger_id: trigger_id,
    view: JSON.stringify(modal)
  };

  const result = await axios.post('/views.open', qs.stringify(args));
};

The code snippet seems long, but as you can see, the code is mostly just constructing a JSON for the form UI! See how it is built on Block Kit Builder.

Handling the form submission

The submission from a user is handled in the same way the button click from the Home tab was handled.

When the form in the modal is submitted, a payload is sent to the same endpoint of the action. You can differentiate the submission by checking the type in the payload data. (To see the full code, see the lines 107 - 133 in index.js):

app.post('/slack/actions', async(req, res) => {
  const { type, user, view } = JSON.parse(req.body.payload);
  else if(type === 'view_submission') {
    res.send(''); // Make sure to respond to the server to avoid an error

    const data = {
      note: view.state.values.note01.content.value,
      color: view.state.values.note02.color.selected_option.value
    }
    displayHome(user.id, data);
  }
});

Updating the App Home view

Then append the newly acquired data from the user to the current view block, and rerender the Home tab view using views.publish.

In this example app, I am using a simple persistent database with the node-json-db module. Each time a user adds a new note, the data is pushed to the data array. I am creating a new data block in JSON then append to the existing JSON, then display the new view by calling the views.publish.

You can see the source code in lines 17-152 in appHome.js, but this is up to you how you want to achieve this flow.

Trying your app

Now your app should be working. To enable it, go to your Slack workspace, click Apps from the sidebar menu, where you should see a list of all installed apps, and click your app. See how App Home work by playing around with the app!

Achieving better user-experiences

I hope this tutorial gave you good ideas on how you can use App Home for your existing app or a whole new app!

This tutorial only covered the fundamental parts of building an App Home experience using views methods and the modal, but in the next tutorial, Shay DeWael will explain the design best practices by extending this Stickies App to make it more practical so stay tuned!

Questions? Comments? Ask me, Tomomi @girlie_mac or @SlackAPI.