How to get automatically local backend url in __DEV__?

Expo SDK
1

Hi,

I’d like to avoid managing my api url with environment variables.

Formerly I was using this code in DEV which worked fine in Expo client:

const { hostname } = url.parse(NativeModules.SourceCode.scriptURL);
const backendUrl = http://${hostname}:10400;

However now I’ve detached and run with XCode / Android Studio, on emulators or device and the above code does not work in such scenarios, leading to a backend url like “http://packager.qv-rrd.slorber.photographers.exp.direct:10400”

I was wondering if there was any cross-platform (android/ios/expo-client/emulators) that would permit me to easily get my api url (which runs in the same computer I run “exp start” on)

Thanks

2

Hi, try examining the contents of Expo.Constants.manifest, which will contain information about where the app is being served from.

Whether in ExpoKit or not, you can always exp start --localhost or exp start --lan to switch the kind of development url generated by your exp instance.

3

thanks I didn’t know about these cli options :slight_smile: will try that asap

4

Not sure it’s normal but I got this error with “exp start --lan” (but it’s still working fine, just unexpected error msg)

[exp] Error starting tunnel: XDLError: failed to start tunnel

(edit: it seems on second command run I don’t get this error now, maybe I made a mistake?)

5

Also worth mentionning I could not get --localhost option to work in Android simulator, in which usecase is it supposed to work? --lan option seems to work fine on phone/simulator (as long as phone is on same wifi network) so I wonder why I would use localhost instead of always using --lan?

6

hey @slorber, --localhost will only work in the android simulator if you run adb reverse first

7

thanks, I’ll stick to --lan as a default as it seems to be the thing that works most easily in all the situations I want :wink: