If you need to make 4 API calls concurrently but 1 of the AP

Question

If you need to make 4 API calls concurrently but 1 of the API calls depends on data from another What would be the best pattern

Remy Benza · Answer

```fun getLiveGameData viewScope CoroutineScope viewScope launch <http Dispatchers IO|Dispatchers IO> while isActive make the 4 API calls concurrently val fixture = async payPerViewRepository getNextFixture val liveVideo = async payPerViewRepository getPPVLiveVideo liveVideo val showLiveGame = async payPerViewRepository getPPVToggle showVideo == 1 val liveMatchInfo = async get id from Fixture first to make API call for live info val matchId = fixture await id orEmpty payPerViewRepository getLiveMatchInfo matchId val data = PayPerViewLiveGame liveVideo = liveVideo await fixture = fixture await liveMatchInfo = liveMatchInfo await showVideoPlayer = showLiveGame await liveGameData postValue data delay Duration ofSeconds 10 toMillis poll every 10 secs ```

Remy Benza · Answer

my current code arrow up

Remy Benza · Answer

the 4th API call `liveMatchInfo` relies on the first API call that returns a `fixture` object

Remy Benza · Answer

is this a good pattern or should I just use something like this ``` val liveVideo = async payPerViewRepository getPPVLiveVideo liveVideo val showLiveGame = async payPerViewRepository getPPVToggle showVideo == 1 val fixture = payPerViewRepository getNextFixture suspend here to wait for result val liveMatchInfo = async get id from Fixture first to make API call for live info val matchId = fixture id orEmpty payPerViewRepository getLiveMatchInfo matchId ```

Remy Benza · Answer

In that case the coroutine will suspend until `payPerViewRepository getNextFixture ` returns

Remy Benza · Answer

so maybe less performant

krzysztof · Answer

what about moving `fixture` to same async call where it is needed as argument ```val liveMatchInfo = async val fixture = payPerViewRepository getNextFixture val matchId = fixture id orEmpty payPerViewRepository getLiveMatchInfo matchId ```

Remy Benza · Answer

then async no longer returns deferred

christophsturm · Answer

i think all 3 versions perform the same

krzysztof · Answer

gt then async no longer returns deferred Not exactly following You mean call to `async ` won t return you Deferred

Remy Benza · Answer

I need the fixture object outside of the asycn scope too

krzysztof · Answer

ah make sense haven t notices it s required in other `async` too

krzysztof · Answer

then I think like Christoph said it d perform the same

christophsturm · Answer

i think the most readable version is to make only the `liveVideo` and `showLiveGame` calls async

Remy Benza · Answer

I have this now

christophsturm · Answer

hmm but that code assumes that await returns null when its not ready but await waits until the result is ready

Remy Benza · Answer

all API calls return null when an error comes back

christophsturm · Answer

ah ok

Remy Benza · Answer

maybe `liveMatchInfo`doesn t need to be an async coroutine

christophsturm · Answer

you can just make liveMatchInfo not async because you start it async and then await it

Remy Benza · Answer

since it s the last call and `liveVideo` and `showLiveGame` are already running concurrently right

christophsturm · Answer

or in other words because `async xxx await ` is the same as `xxx `

Remy Benza · Answer

yes true Thnx

ursus · Answer

Why not treat it as 3 concurrent ones

Remy Benza · Answer

whats your suggestion to make it better

ursus · Answer

I didnt read the whole thing but Id treat it as `concurrent a b sequential c d `

uli · Answer

I d go with the first version as it is most straight forward all four async all four awaited where ever they are needed No deeper knowledge about any details needed to understand what s going on No reasoning why one of those can be just a suspend call No reasoning to break if you change the order of fiering those requests