Exchange order

[lsarni]

We are having some glitches on how the data is loaded, and I wonder if we might not have our exchanges in the correct order. I think it would be really useful to document the correct order in a single place. I see on the authentication docs The authExchange is an asynchronous exchange, so it must be placed in front of all fetchExchanges but after all other synchronous exchanges, like the cacheExchange. but then it's not always stated if an exchange is async or sync, or where should it go on the list.

In particular we have

• devtoolsExchange
• authExchange
• requestPolicyExchange
• offlineExchange
• fetchExchange

Is this order correct?

[lsarni]

I just found this explaining the order, but I'm not sure I know which ones are sync/asycn https://commerce.nearform.com/open-source/urql/docs/advanced/authoring-exchanges/#synchronous-first-asynchronous-last

[JoviDeCroock]

In your case you want

devtoolsExchange <-- debugging
requestPolicyExchange <-- synchronous changes to the context
offlineExchange <-- synchronous access to the cache
authExchange <-- asynchronous, can do requests to renewAuth/...
fetchExchange <-- asynchronous, reaches out to your back-end

[lsarni]

Thanks for the quick reply!

Our offlineExchange uses AsyncStorage https://commerce.nearform.com/open-source/urql/docs/graphcache/offline/#react-native does that make it async?

[JoviDeCroock]

No rehydration happens in the background. A cache has a synchronous need as you don't want to delay load-unload by a micro-tick due to implicit Promises.

[lsarni]

Thank you again :)