```override suspend fun getProducts =flow lt State lt List l

Question

```override suspend fun getProducts =flow lt State lt List lt ProductListFromEntity gt gt gt try val it = productDao getProducts if it isEmpty loadProducts else emit State success it catch e Exception emit State error e localizedMessage toString e printStackTrace Dao function Query SELECT product productId product productCode product name FROM Product product abstract suspend fun getProducts List lt ProductListFromEntity gt viewModel suspend fun getProducts productRepository getProducts collectLatest when it is State Error gt productListStates value = ProductListStates Error it message UIComponentType Dialog is State Success gt parseGivenProductList it data ``` i am calling this function from viewmodel android But it is always throwing error saying `Child of the scoped flow was cancelled` without any stacktrace Am i doing anything wrong here

gildor · Answer

gt without any stacktrace It s strange it should have at least some stacktrace could you show full error message

gildor · Answer

I m not quite sure how you use `productDao getProducts ` as I understand from your example it should return Flow but you use it a way that it returns List

Noushad Chullian · Answer

When i am copying here i was trying to change somthing else that is why it is returning a flow here i will edit the question

gildor · Answer

When you run this code could you show full error message

gildor · Answer

For example instead of doing `State error e localizedMessage toString ` pass whole exception ```State error e ```

Noushad Chullian · Answer

Okay

gildor · Answer

otherwise for now it looks that it can hide some error for example just by hiding `cause`

Noushad Chullian · Answer

`kotlinx coroutines flow internal ChildCancelledException Child of the scoped flow was cancelled` this is the Exception returning no stackTrace found

gildor · Answer

It doesn t look as full exceptiuon

gildor · Answer

it looks as exception toString

Noushad Chullian · Answer

yes But that is the only thing iam getting

gildor · Answer

well exception toString is not a full exception make sure that you print stacktrace too

gildor · Answer

actual exception has some stacktrace anyway

gildor · Answer

With code you provided there is no way to understand what is going on and which part of your code is actually throwing it and who is handling it

gildor · Answer

So which part of code catches this exception

gildor · Answer

Open `cause` and check maybe there is stacktrace

Noushad Chullian · Answer

i thought it is because of any error in Room library but i tried with network call in the same and same error

gildor · Answer

Just checking what `loadProducts` is doing there is no related code in your example

Noushad Chullian · Answer

So which part of code catches this exception when executing `productDao getProducts `

gildor · Answer

Ah I probably got it it just means that flow where you run this code is already cancelled

Noushad Chullian · Answer

`loadProducts` is a network call to fetch from server and it is working because iam using that one to store into my sqlite

gildor · Answer

on practice it probably means that scope where you call viewModel getProducts is already cacncelled

Noushad Chullian · Answer

Ah I probably got it it just means that flow where you run this code is already cancelled can you please explain that

gildor · Answer

flow is active only while someone is collecting it

gildor · Answer

if coroutine which collects this flow is cancelled you will get this exception every time when you call any suspend function

gildor · Answer

The right way would be instead of ``` catch e Exception ``` do ``` catch e CancellationException throw e catch e Exception ```

gildor · Answer

so it will propagate cancellation

Noushad Chullian · Answer

Okay thanks LEt me try

Noushad Chullian · Answer

so meaning this getProducts from repository is running viewModelScope

gildor · Answer

It s opposite viewModel getProducts collecting your productRepository getProducts so it depends on where this viewModel getProducts is called

Noushad Chullian · Answer

confused now so which of my scope is cancelled the flow from repository

gildor · Answer

no scope on which viewModel getProducts is called

gildor · Answer

So in general there is no issue in code which you show except that you do not propagate cancellation and end up with State Error with cancellation error which you usually don t want to have you want instead propagate cancellation But it doesn t solve your issue it looks that your problem not with this code but with the fact that something cancelling your viewModel getProducts

gildor · Answer

gt `loadProducts` is a network call to fetch from server and it is working because iam using that one to store into my sqlite But as I see it doesn t emit anything looks that you return nothing there

Noushad Chullian · Answer

yes the dao call must be flowable that is how it was and i was trying to find this thing so for now i changed not to flow

gildor · Answer

Well if dao is flowable it will be very different code

gildor · Answer

and I just don t understand how it supose to work

Noushad Chullian · Answer

yes

gildor · Answer

probably you need something like thius ```if it isEmpty emit State success loadProducts else emit State success it ```

Noushad Chullian · Answer

``` this is how i am calling viewmodel to load lifecycleScope launchWhenStarted vm action emit ProductListActions FetchProductList the init of viewmodel init viewModelScope launch handleIntent private suspend fun handleIntent action collectLatest when it ProductListActions FetchProductList gt getProducts ```

Noushad Chullian · Answer

is there anything wrong here

Noushad Chullian · Answer

because i am using the same way in another place and it is working like expected

gildor · Answer

It can be related on the fact that you use collectLatest everywhere which cancells coroutine so every new action will cancell currently running getPRoducts

gildor · Answer

it s not an issue if you propagate cancellation correctly as I suggested above

Noushad Chullian · Answer

THanaks Brother

gildor · Answer

Hope it will help

gildor · Answer

I would also suggest you instead of `flow lt State lt List lt ProductListFromEntity gt gt gt ` to use simple map catch on flow it would be more natural code and more flexible and will easily work with flow

Noushad Chullian · Answer

like how

gildor · Answer

I mean implement this function as mapping of values

Noushad Chullian · Answer

THanks I will try

gildor · Answer

depend of course on how productDao getProducts is implemented now there is no reason to use Flow there it always return one value

Noushad Chullian · Answer

yea but i will make the query back to flow

gildor · Answer

even with current suspend function it can be implemented like ```productDao getProducts toFlow convert reference on suspend function to flow later you can just use any other flow map if it isEmpty loadProducts Suppose it returns State else State success it catch emit State error ```

Noushad Chullian · Answer

THanks Can i ask another question

Noushad Chullian · Answer

since i am struggling with this flow collect thing

Noushad Chullian · Answer

`private suspend fun handleIntent ` `action collectLatest ` `when it ` `ProductListActions FetchProductList gt ` `getProducts ` ` ` ` ` ` ` this function has another events but when i am using just collect it is not collecting from second time it is working for only first time any idea about that

gildor · Answer

Is it with flow or suspend function on DAO

gildor · Answer

because when youy change dao to flow it never complete it will be subscribed forever as result getProducts function never return and can be cancelled

Noushad Chullian · Answer

no from fragment activity to viewmodel

gildor · Answer

not sure what you mean

gildor · Answer

I just said that your current implementation will work very different with suspend or with dao

gildor · Answer

it shouldn t be an issue about collect if you use suspend function

gildor · Answer

but it will be with Flow

Noushad Chullian · Answer

i am passing action via sharedFlow from activity to viewModel and i am collecting it here `private suspend fun handleIntent ` `action collect ` `when it ` `ProductListActions FetchProductList gt ` `getProducts ` ` ` ` ` ` ` But for the first time the sharedFlow is collected and not collecting afterwards

gildor · Answer

Sorry it hard to understand what is going on which this example

Noushad Chullian · Answer

it is not related to my first question

Noushad Chullian · Answer

this is a different one

Noushad Chullian · Answer

i am passing action via sharedFlow from activity to viewModel and i am collecting it here `private suspend fun handleIntent ` `action collect ` `when it ` `ProductListActions FetchProductList gt ` `getProducts ` ` ` ` ` ` ` But for the first time the sharedFlow is collected and not collecting afterwards

Noushad Chullian · Answer

this `handleIntent ` is called from the init of the viewModel So I am thinking the collecting of action inside ths function will persist till the viewModelScope is alive

gildor · Answer

gt it is not related to my first question I understand and I have even less context so don t understand what is going on there

Noushad Chullian · Answer

Emiting action from activity fragment works for the first time like getProgucts but second time when clicked on the product from the list i am passing another action to viewmodel about this click event but it is not collecting

gildor · Answer

I already told you it depends on how getProducts implemented

Noushad Chullian · Answer

THanks Now I understtod

Noushad Chullian · Answer

THank you for clearing my doubts

Nick Allen · Answer

FYI you should pretty much never call emit from try catch See <https kotlinlang org docs flow html exception transparency|https kotlinlang org docs flow html exception transparency>

Noushad Chullian · Answer

THanks