Create an App

In this document, you will learn about the Apps-Engine commands and create a basic app.

Apps-Engine CLI commands

rc-apps is a command-line interface (CLI) utility that provides commands to rapidly develop a Rocket.Chat application. Initiate rc-apps in your terminal to view the list of commands that you can execute as needed.

Here is a list of commands that Rocket.Chat Apps-Engine supports:

Create a basic app

Now that you've understood the basic concepts of the Apps-Engine and installed the CLI, let's build our first example Hello World app .

Make sure that you have the setup environment ready.

Step 1: Execute the create command

To create a new app, in the command line, execute rc-apps create.

Enter the following app details:

• App Name: Hello World

• App Description: A basic app that prints Hello World!

• Author’s Name: John

• Author’s Home Page: rocketchat.com

• Author’s Support Page: support.rocketchat.com

A folder with the app name is created in the current working directory (in this case, hello-world). The hello-world folder contains a simple app that will only compile and be packaged in the dist folder.

Troubleshooting tip

If you receive the error message 'TypeError: Cannot read properties of undefined [reading 'message']', do not be alarmed. You can disregard this and use the cd <folder-name> command to determine if a folder for your application was created.

Step 2: Open the app folder in Visual Studio

1. Launch Visual Studio and select Open Folder from the sidebar on the left.

2. Select the app folder that was created in the previous step.

3. Once the folder has been uploaded, its contents will be displayed in the sidebar.

Step 3: Comprehend the structure of the app

• The app manifest file app.json contains basic details about the app:

{
    "id": "28d63257-94c3-40e8-83eb-9581244598b6",
    "version": "0.0.1",
    "requiredApiVersion": "^1.4.0",
    "iconFile": "icon.png",
    "author": {
        "name": "John",
        "homepage": "rocketchat.com",
        "support": "support.rocketchat.com"
    },
    "name": "Hello World",
    "nameSlug": "hello-world",
    "classFile": "HelloWorldApp.ts",
    "description": "A basic app that prints Hello World!"
}

• A Rocket.Chat app is a TypeScript project that contains a main file with a class extending the main App class from the Apps-Engine. The identity of this file can be found in the classFile property of your app.json file. For this example, locate and open the HelloWorldApp.ts TypeScript file.

• The following code snippet shows the class in the HelloWorldApp.ts file:

export class HelloWorldApp extends App {
    constructor(info: IAppInfo, logger: ILogger, accessors: IAppAccessors) {
        super(info, logger, accessors);
    }
}

• Observe that the class name and filename are identical. This is intentional. You can either use the same name for the class and the file for the application to compile successfully, or export the primary app class by default as shown below:

export default class HelloWorldApp extends App {
    // ...
}

• For a functioning app, you must define a constructor to access a large number of parent properties. The constructor accepts three arguments:

  • An IAppInfo object: This object contains fundamental information about your application, such as its name, version, description, etc. It is private to the App class, but its properties are accessible through multiple GET methods.

  • An ILogger object: This object is the interface for logging. The getLogger() method allows access to this object from within a child class.

  • An IAppAccessors object: This object contains all app accessors. This can be accessed via the getAccessors() method in the child class.

Learn more about the module details from the Rocket.Chat Apps Typescript definition.

Step 4: Implement the app functionality

For this example, the app records "Hello, World!" in the Rocket.Chat administration interface.

To log data, you must first have access to the logger, that is, an object of type ILogger. The parent class logs data to the administration interface using an ILogger object. We only require access to this object. Since the logger object is private to the App class, the this keyword cannot be used to access it directly.

To resolve this, use the getLogger method provided by the App class. You need to store the logger as a separate object that can be reused whenever necessary.

Modify the class in the HelloWorldApp.ts file as follows:

export class HelloWorldApp extends App {
    private readonly appLogger: ILogger
    
    constructor(info: IAppInfo, logger: ILogger, accessors: IAppAccessors) {
        super(info, logger, accessors)
        this.appLogger = this.getLogger()
    }
}

We have just stored the accessor for the log file in the appLogger variable. Now, we can record anything with it. Add the line shown below to the constructor and save the file.

this.appLogger.debug('Hello, World!')

Step 5: Deploy to the server

In the command line, go to the hello-world app folder that was created in Step 1: Execute the create command. To deploy the app, run:

rc-apps deploy --url <server_url> -u <user> -p <pwd>

• Replace <server_url> with the URL of your Rocket.Chat workspace.

• Replace <user> and <pwd> with your username and password, respectively.

After executing this command, your application will be deployed to the server.

To explore alternative authentication options for deploying your app, such as using 2FA codes or personal access tokens, run the  rc-apps deploy --help  command.

Packaging your app

Alternatively, you can execute the rc-apps package command. This gives you a compressed zip file of your app that you can upload as a private app to your Rocket.Chat server.

Step 6: Test the app

To test your app, you need a Rocket.Chat server running locally on your machine and the credentials of an administrator user.

In older versions of Rocket.Chat, you might need to enable apps development mode for manual installations to be allowed.

To enable apps development mode:

• Go to Administration > General > Apps.

• Click True next to Enable development mode.

To run Rocket.Chat in develop mode, see the development environment setup guide.

In this example, the function of the application is to log Hello, World! to the console. To test the app's functionality, we must examine the app logs.

Follow these steps to examine the logs:

1. Login to your Rocket.Chat workspace as an admin.

2. Navigate to the Administration Panel.

3. Under Apps, select Marketplace.

4. Select Private Apps from the left-hand menu. You should see the Hello World app.

5. Click on the three dots icon on the right-hand side of the app. From the menu, click on View Logs.

6. The App Info page opens on the Logs tab. Scroll down until you see the "constructor" expandable section. Select it and you can see the message "Hello, World!" logged in the console.

Congratulations, you just created your first app — a simple Hello World app!

To learn how to add more functionalities to your app, proceed to the next topic.

Troubleshooting