Question on ktor + exposed + coroutines

# ktor

[waltermcq]

Question on ktor + exposed + coroutines

[waltermcq]

I'm trying to insert a new user into my database using the exposed DSL, with transactions that are wrapped with coroutines e.g. the dqQuery {} method frequently found for this purpose

[waltermcq]

Here's basically what the insert function is:

override suspend fun newUser(id: String, name: String): UserAgg {
        return dbQuery {
            val userRow = UserTable.insert {
                it[this.id] = id
                it[this.name] = name
            }.resultedValues!!.first()

          getUserById(UserId(userRow[UserTable.id]))!!
        }
    }

[waltermcq]

Heres's dbQuery()

suspend fun <T> dbQuery(
    block: () -> T): T =
    withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
        transaction { block() }
    }

[waltermcq]

The issue is in the insert newUser function, when I call getUserById to get the new id (specifically, a uuid) from the database, intellij tells me that getUserById must be called within a coroutine body

[waltermcq]

I can't wrap it in a dbQuery() call, I get the same issue (as its apparently not a coroutine body)

[waltermcq]

what is the best way to call getUserById() given the need for a coroutine body?

[tjohnn]

You have to call it in a ktor route{}.

[tjohnn]

Or if you want to call it from another function , maybe repository function, mark that function as suspending and call that function from inside a route{}

[Magno Junior]

maybe:

suspend fun <T> dbQuery(
    block: suspend () -> T): T =
    withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
        transaction { block() }
    }

but I am not sure all these functions has to be suspend 🤔

[waltermcq]

@tjohnn Can you clarify why I would be using a ktor route specifically for a DB call? I'm not understanding the connection between the ktor route and a coroutine...

[waltermcq]

@Magno Junior my understanding is that this is a common pattern to use coroutines when using exposed - they need to be suspending functions

[tjohnn]

I think you got it wrong. dbQuery is suspending so it has to be called in another suspending function or within a coroutine scope. Ktor routes are in a coroutine scope that helps them to run tasks concurrently.

[tjohnn]

https://ktor.io/quickstart/coroutines.html

[tjohnn]

And oh I see you need to mark block() as suspending

[waltermcq]

okay - what's the proper way to do that?

[waltermcq]

if I markup the above

block: () -> T): T =

to

block: suspend () -> T): T =

then the block() inside the transaction{} now requires a coroutine body

[Sourabh Rawat]

did you try runBlocking ?