Environment Variables

The table below lays out environment variables for the Lexicon Mobile App.

If there is a default value indicated, you do not need to set it.

Environment Variable	Required	Notes	Default Value	Example Value
MOBILE_PROSE_HOST	Yes	The hostname of the Prose Server (must start with http or https)	-	https://prose.myserver.com
MOBILE_PROSE_PORT	No	The port of the Prose Server	(empty)	8080

MOBILE_PROSE_HOST

Note that MOBILE_PROSE_HOST must always be specified, and must always start with either http:// or https://.

Otherwise The Lexicon Mobile App has no idea what server to talk to in order to interact with Discourse.

Different Behavior in Development

If the Mobile App detects that NODE_ENV is not production, then it will adjust its behavior slightly if MOBILE_PROSE_HOST is making use of localhost or 127.0.0.1.

In this case, a replacement will be made using Expo's debuggerHost constant, which is used to locate the IP address of your development machine.

This addresses multiple issues:

• Accessing localhost from within the Android simulator does not map to your development machine
• Accessing localhost from a device running Expo Go does not map to your development machine, requiring you to manually identify and specify your development machine's IP address with MOBILE_PROSE_HOST.

If you are interested in more details about this, the implementation of this behavior is available in frontend/constants/app.ts.

MOBILE_PROSE_PORT

MOBILE_PROSE_PORT is used to allow explicitly specifying the port number.

MOBILE_PROSE_HOST=http://localhost
MOBILE_PROSE_PORT=8999

If it is not set, only MOBILE_PROSE_HOST will be used to derive the host of the Prose

This presents a situation where you could omit MOBILE_PROSE_PORT and still specify a port number, if you desired:

MOBILE_PROSE_HOST=http://localhost:8999