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Writing Your First Custom Component

In this tutorial we will create a Slack component from scratch to illustrate how readily you can write custom code for an integration.

Initialize your project#

Suppose Prismatic's Slack component did not exist. How would one go about creating a component that sends notifications to Slack?

To start your integration, use the prism components:init subcommand to create a new TypeScript project.

# Initialize the projectprism components:init myslack
Creating component directory for "myslack"...? Description of Component: My Slack Component? Type of Connection: Basic Connection   create package.json   create assets/icon.png   create src/index.ts   create src/index.test.ts   create src/client.ts   create jest.config.js   create tsconfig.json   create webpack.config.js   create src/actions.ts   create src/triggers.ts   create src/connections.ts
# Move to the newly created directorycd myslack
# Pull down the Slack icon for use by the componentcurl '' > assets/icon.png
# Remove all boilerplate code; we'll write this component from scratchrm src/*.ts

This will create a NodeJS project with TypeScript support, complete with required dependencies, like Webpack and Prismatic's custom component library, spectral.

Add dependencies#

Most of the dependencies you require have been added for you, but because you're building a Slack component, you will want to take advantage of the Slack webhook npm package.

npm install @slack/webhook

Add the following to the top of a new file, src/index.ts:

import { action, component, input, util } from "@prismatic-io/spectral";import { IncomingWebhook } from "@slack/webhook";

Create some input fields#

What information will you need to send a Slack message? At minimum, we'll need two things:

  1. A Slack webhook URL to send messages to
  2. A message to send.

To create those input fields for your component, you will create two new inputs in src/index.ts. The label and placeholder will appear within the Prismatic web app when a user utilizes this action. type and required are self-explanatory.

Each input has a clean function, which helps with type hinting - the util.types.toString function will guarantee that the value of webhookUrl and message is cast to a string.

const webhookUrl = input({  label: "Webhook URL",  placeholder: "Slack Webhook URL",  type: "string",  required: true,  clean: util.types.toString,});const message = input({  label: "Message",  placeholder: "Message to send",  type: "string",  required: true,  clean: util.types.toString,});

Create a component action#

Now it's time to create an action that our component can take. You need to provide the action with a label and description to display in the web app, a set of inputs that you created above, and some code to perform when the action is invoked. You can take advantage of the Slack API in our perform function.

const postSlackMessage = action({  display: {    label: "Slack Message",    description: "Post a message to a Slack channel",  },  perform: async (context, params) => {    const webhook = new IncomingWebhook(params.webhookUrl);    const result = await webhook.send({ text: params.message });    return { data: result };  },  inputs: { webhookUrl, message },});

Export your component#

Lastly, we need to export a component object that has a unique key to identify it in Prismatic, contains a label and description to display in the web app, and an object containing the actions that are associated with the component.

export default component({  key: "newSlack",  public: false,  display: {    label: "New Slack",    description: "Post messages to Slack",    iconPath: "icon.png",  },  actions: { postSlackMessage },});

Build and deploy your component#

At this point you're ready to compile your component, and then deploy it. The build script leverages webpack to compile and minify your TypeScript:

npm run build

Your build exists in dist/. Now, you can use prism to deploy your component.

prism components:publish

Test your new component#

Congratulations! You've published your first custom component! Try modifying your first integration to use your new component, and verify that it posts to Slack like the official Prismatic Slack component does!