Does Anyone Know How to do Networking Effects with Combine in the TCA architecture ?

[Dominic263]

Hi folks,

I am having a challenge when it comes to doing any networking using combine for my mock TCA app. I decided to learn TCA by actually building a project a few weeks ago but I am having issues with network effects. I am trying to fetch data from https://catfact.ninja/facts to display cat facts in the app, and I have somehow realized that there is an error happening because the replaceError(with: ) function is being invoked every time I fetch data.
This is how I modeled my Data as per the schema from the site I am trying to execute the get request.

and this is the snippet of code from my reducer which shows how I try to fetch data using URLSession

Is there something I am doing wrong here and if so how can I correct that? Thanks for your help and let me know if I should provide more information.

[stephencelis]

@Dominic263 Looking at the JSON payload, I think the issue is you are trying to decode [CatFact].self from a response that nests that array ({"data":[...],...}). That means you need an additional wrapper type:

struct CatFactResponse: Decodable {
  var data: [CatFact]
}

Which you can use when you call .decode on the Combine publisher.

A couple notes on debugging tips:

If you call .print() on the publisher before .replaceError, you should get info about the error in the console, which will probably be a decoding error:

.print()
.replaceError(with: [...])

[Dominic263]

works like magic. Thanks, Stephen!

[Dominic263]

with regards to debugging, I am also a newbie in Xcode and I tried to insert the print statement before replacerError but it doesn't seem to work. Nothing prints out in the Debug area. I tried as well to go to View > DebugArea > Activate Console, then built and ran my project but when I execute fetch by tapping the stats button there are no print statements shown. Am missing something?

[stephencelis]

@Dominic263 I think we'd need to see the exact publisher code and more screenshots to debug further, sorry!