App

The essential concepts of a Homey App.

On this page we will look at what the various files in the Homey app folder are for and what essential concepts you should be aware of to start developing your Homey app.

Apps are able to use all of Homey's capabilities and thus can use the following technologies:

Most Apps use only one wireless technology but it is possible to use them all at the same time in a single Homey App. Regardless of the wireless technologies used in your Homey app most of the concepts are the same. Every Homey app has the same basic file structure:

com.athom.example/
├─ .homeycompose/
│ ├─ app.json
│ └─ ...
├─ assets/
│ ├─ icon.svg
│ └─ images
│ ├─ small.png
│ ├─ large.png
│ └─ xlarge.png
├─ drivers/
│ ├─ my_driver/
│ │ ├─ assets/
│ │ │ ├─ icon.svg
│ │ │ └─ images/
│ │ │ ├─ small.png
│ │ │ ├─ large.png
│ │ │ └─ xlarge.png
│ │ ├─ device.js
│ │ └─ driver.js
│ └─ ...
├─ locales/
│ ├─ en.json
│ └─ nl.json
├─ settings/
│ └─ index.html
├─ api.js
├─ app.js
├─ app.json
├─ env.json
└─ README.txt

App Manifest

The /app.json file is the complete app manifest, it tells Homey what your app does. When you run or publish your app this file is generated from the various *.compose.json files and the JSON files in the /.homeycompose/ folder. The generation of your app manifest is referred to as Homey Compose and it supports some additional advanced features such as templating. All the various compose files will be explained in the rest of the documentation.

All basic information about your app is configured in the /.homeycompose/app.json file. You can read the App Manifest documentation to learn more about this file.

Because the /app.json file gets generated from the various Homey Compose files you should never manually edit it. You should edit the *.compose.json and JSON files in the /.homeycompose/ folder instead.

App Class

In the /app.js file you can create an App class. This class gets instantiated once, when your app started. This is a great place to put logic that is shared throughout your app, and it is sometimes necessary for Flow cards and other resources that you only want to setup once.

The app instance can be accessed from your Driver and Device classes through this.homey.app.

/app.js
const Homey = require('homey');
const ApiClient = require('your-external-api-client');
class App extends Homey.App {
async onInit() {
// create an ApiClient once when the app is started
this.client = new ApiClient();
}
}
module.exports = App;
/drivers/<driver_id>/device.js
const Homey = require('homey');
class Device extends Homey.Device {
async onInit() {
// access the ApiClient through the App instance
const data = await this.homey.app.client.getData();
}
}
module.exports = Device;

App API

Homey apps can expose an API that other devices can talk to. It is even possible for Homey apps to talk to each other by exposing an API. The /api.js file contains the implementation of all the API endpoints. You can read about exposing an API from your App in the Web API guide.

Assets

In the /assets/ folder at the root of your app you can put the assets of the app. These are the app icon icon.svg and the app images that will be shown in the Homey App Store. Read the App Store guidelines for more information about the icon and images.

Drivers and Devices

The /drivers/ folder contains all the drivers of your app. The drivers are the parts of a Homey app that allow users to add and then control devices. This folder should only contain other folders, it is common for those folders to be named after the product code of the device they are implementing. You can learn more by reading the Devices documentation.

Locales

Translation files are kept in the /locales/ directory. You can learn more about these files by reading the internationalization documentation.

Readme

The /README.txt file in the root of your app contains the long-form description of your app. This will be shown in the Homey App Store when a user is browsing your app. Read the App Store guidelines for more information about the readme.

You can supply translated versions of the readme by naming the file README.<languagecode>.txt, for example README.nl.txt would contain the Dutch translation of the readme. You can find the supported languages in the internationalization documentation.

Settings

In your Homey app you can save settings that are persistent across reboots. These settings can be accessed from anywhere in your app through ManagerSettings.

/app.js
const Homey = require('homey');
class App extends Homey.App {
async onInit() {
const username = this.homey.settings.get('username');
// ...
}
}
module.exports = App;

You can also create a page where users can update the App Settings by creating an index.html file in the /settings/ folder. Since drivers have their own settings, most apps shouldn't need any App settings. Read more about how and when to use app settings in the App Settings guide.

Environment

The /env.json file in the root of your app contains the environment variables of your app. Since this file is usually used to store secret keys it should be kept on your computer. If you use Git the /env.json file should therefore be added to the /.gitignore file. In this file you can store information that should not be public, for example the OAuth2 tokens your app uses to connect to a cloud service.

/env.json
{
"CLIENT_ID": "12345abcde",
"CLIENT_SECRET": "182hr2389r824ilikepie1302r0832"
}

The variables are available anywhere in your app under Homey.env.CLIENT_ID, Homey.env.CLIENT_SECRET, etc. Make sure they are uppercase, and that their value is a string.

const Homey = require('homey');
const CLIENT_ID = Homey.env.CLIENT_ID;
const CLIENT_SECRET = Homey.env.CLIENT_SECRET;

These variables are stored on Homey, and in theory should not be readable by anyone. However, make sure that these variables alone do not provide access to private resources.

Homey Ignore

The /.homeyignore file in the root of your app can be used to prevent certain files or folders from being included in your Homey App when publishing. It works in the same way as .gitignore. By default all files in the app directory will be included when publishing your Homey App. /.homeyignore is useful in case you want to commit documentation, designs, images, etc. to your version control system but not include it in your Homey App when publishing.

/.homeyignore
comments.txt
docs/*