# R Shiny Example Web App

[View full source code on GitHub](https://github.com/dnanexus/dnanexus-example-applets/tree/master/Tutorials/bash/r-shiny-web-app)

## Creating the web application

Inside the `dxapp.json`, you would add `"httpsApp": {"ports":[443], "shared_access": "VIEW"}` to tell the worker to expose this port.

R Shiny needs two scripts, `server.R` and `ui.R`, which should be under `resources/home/dnanexus/my_app/`. When a job starts based on this applet, the `resources` directory is copied onto the worker, and since the `~/` path on the worker is `/home/dnanexus`, that means you have `~/my_app` with those two scripts inside.

From the main applet script `code.sh`, start shiny pointing to `~/my_app`, serving its mini-application on port 443.

```shell
main() {
  R -e "shiny::runApp('~/my_app', host='0.0.0.0', port=443)"
}
```

For all web apps, if everything is running smoothly and no errors are encountered (the ideal case), the line of code that starts the server keeps it running indefinitely. The applet stops only when it is terminated. This also means that any lines of code after the server starts are not executed.

## Modifying this example for your own applet

To make your own applet with R Shiny, copy the source code from this example and modify `server.R` and `ui.R` inside `resources/home/dnanexus/my_app`.

### How to rebuild the shiny asset

[View `dxasset.json` file](https://github.com/dnanexus/dnanexus-example-applets/blob/master/Tutorials/bash/shiny-asset/dxasset.json)

To build the asset, run the `dx build_asset` command and pass `shiny-asset`, that is the name of the directory holding `dxasset.json`:

```shell
dx build_asset shiny-asset
```

This outputs a record ID `record-xxxx` that you can then put into the applet's `dxapp.json` in place of the existing one:

```json
"runSpec": {
    ...
    "assetDepends": [
    {
      "id": "record-xxxx
    }
  ]
    ...
}
```

### Build the applet

Build and run the applet itself:

```shell
dx build -f dash-web-app
dx run dash-web-app
```

Once it spins up, you can go to that job's designated URL based on its job ID, `https://job-xxxx.dnanexus.cloud/`, to see the result.