Hi all :android-wave: , How to combine and collect...

# compose-android

[Abhimanyu]

Hi all 👋 ,
How to combine and collect multiple flows in a type safe way?

Current code

combine (flow1, flow2, flow3, ...) { data1, data2, data3, ... ->
  DataStructure(data1, data2, data3, ...) // DataStructure would be Pair(), Triple, etc depending on number of flows
}.collectLatest { (data1, data2, data3, ...) ->
   // Can use all data in type safe way
}

As the above code requires DataStructure to be modified for any flow addition or removal from the combine , and also to create new custom DataStructure for more than 3 data.

How can I change this in a type safe way?

combine (flow1, flow2, flow3, ...) { dataList ->
  dataList
}.collectLatest { dataList ->
   // Can NOT use all data in type safe way, the data type is Array<Any?>
}

This code loses the type safety as the data list is Array<Any?> .

[Stylianos Gakis]

What's wrong with the first option?

[Abhimanyu]

I have to create lot of DataStructure classes and it is lot of boiler plate code.

[Abhimanyu]

Also,

the above code requires DataStructure to be modified for any flow addition or removal from the combine

[Stylianos Gakis]

If you really want to, you can make your own combineLatest function, or rather 12 functions or however many parameters you want to combine, which will internally do a combine, create that 1-12 parameter instance, and then pass the items individually inside the lambda.

[Abhimanyu]

Okay, that sounds like a good solution.

So, there is no out of the box solution 😅 ?

[Stylianos Gakis]

Some prior discussions here too https://github.com/Kotlin/kotlinx.coroutines/issues/1484#issuecomment-699600367

They give a solution too, without the data class I was suggesting, but just using the array one and casting appropriately since you know what the types would be in those scenarios

[Stylianos Gakis]

So, there is no out of the box solution

No AFAIK

[Abhimanyu]

Thanks for sharing this. thank you color