Functional way of implementing DB access with additional logic
Currently, my goal is to communicate with DB using CRUD approach. Between simple operation i may have some extra steps (additional business-logic which may throw some errors).
import cats.effect.IO
import scalikejdbc._
IO(NamedDB(MyDB) localTx {
implicit session => {
val x = for {
a <- IO(select()) // Option[Something] (1)
_ <- IO(log(a)) // Option[Something] (2)
_ <- IO(insert()) // Something (3)
_ <- IO(insert()) // Something (4)
c <- IO(select()) // Option[Something] (5)
r <- IO(fileSystemOperation(a, c)) // (6)
_ <- operation(r) // Either[Throwable, Unit] (7)
} yield ()
x.unsafeRunSync() // (8)
}
}).attempt.unsafeRunSync() match { // (9)
case Left(value) => println("Error")
case Right(value) => println("Success") // in reality i want to return some result here
}
The first problem comes in (2): i got error:
Error type mismatch; found : cats.effect.IO[Unit]
required: Option[?]
_ <- IO(log(a))
But if i log result of any insert ((3) or (4)) then all is ok. Probably, it's because of difference in result type Option[Something] vs Something, but i thought that it would be the same as this:
for {
a <- Option(1)
....
}
The second question is how to correcly handle errors in (7) to rollback transaction? Do i have to use pattern matching and do something like this:
operation(r) match {
case Left(e) => throw e
}
or i can throw error inside my operation and return Unit instead of Either[Throwable, Unit]?
Also, i have question about (8) and (9). Is it a correct way to start actual processing and handle any error or not?
I tried to do the same steps using this approach:
select() match {
case Some(_) =>
.....
operation(r) match {
case Left(e) => throw e
case Right(_) => ....
}
case None => ....
}
But in result i got too deep match-case clauses and it was hard to read and understand.
I'm new to FP, but i want to implement this in FP way.
scala functional-programming scala-cats scalikejdbc
asked Nov 20 '18 at 10:07
Nick Ryan
376213
|
show 1 more comment
Currently, my goal is to communicate with DB using CRUD approach. Between simple operation i may have some extra steps (additional business-logic which may throw some errors).
import cats.effect.IO
import scalikejdbc._
IO(NamedDB(MyDB) localTx {
implicit session => {
val x = for {
a <- IO(select()) // Option[Something] (1)
_ <- IO(log(a)) // Option[Something] (2)
_ <- IO(insert()) // Something (3)
_ <- IO(insert()) // Something (4)
c <- IO(select()) // Option[Something] (5)
r <- IO(fileSystemOperation(a, c)) // (6)
_ <- operation(r) // Either[Throwable, Unit] (7)
} yield ()
x.unsafeRunSync() // (8)
}
}).attempt.unsafeRunSync() match { // (9)
case Left(value) => println("Error")
case Right(value) => println("Success") // in reality i want to return some result here
}
The first problem comes in (2): i got error:
Error type mismatch; found : cats.effect.IO[Unit]
required: Option[?]
_ <- IO(log(a))
But if i log result of any insert ((3) or (4)) then all is ok. Probably, it's because of difference in result type Option[Something] vs Something, but i thought that it would be the same as this:
for {
a <- Option(1)
....
}
The second question is how to correcly handle errors in (7) to rollback transaction? Do i have to use pattern matching and do something like this:
operation(r) match {
case Left(e) => throw e
}
or i can throw error inside my operation and return Unit instead of Either[Throwable, Unit]?
Also, i have question about (8) and (9). Is it a correct way to start actual processing and handle any error or not?
I tried to do the same steps using this approach:
select() match {
case Some(_) =>
.....
operation(r) match {
case Left(e) => throw e
case Right(_) => ....
}
case None => ....
}
But in result i got too deep match-case clauses and it was hard to read and understand.
I'm new to FP, but i want to implement this in FP way.
scala functional-programming scala-cats scalikejdbc
asked Nov 20 '18 at 10:07
Nick Ryan
376213
Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
1
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42
|
show 1 more comment
Currently, my goal is to communicate with DB using CRUD approach. Between simple operation i may have some extra steps (additional business-logic which may throw some errors).
import cats.effect.IO
import scalikejdbc._
IO(NamedDB(MyDB) localTx {
implicit session => {
val x = for {
a <- IO(select()) // Option[Something] (1)
_ <- IO(log(a)) // Option[Something] (2)
_ <- IO(insert()) // Something (3)
_ <- IO(insert()) // Something (4)
c <- IO(select()) // Option[Something] (5)
r <- IO(fileSystemOperation(a, c)) // (6)
_ <- operation(r) // Either[Throwable, Unit] (7)
} yield ()
x.unsafeRunSync() // (8)
}
}).attempt.unsafeRunSync() match { // (9)
case Left(value) => println("Error")
case Right(value) => println("Success") // in reality i want to return some result here
}
The first problem comes in (2): i got error:
Error type mismatch; found : cats.effect.IO[Unit]
required: Option[?]
_ <- IO(log(a))
But if i log result of any insert ((3) or (4)) then all is ok. Probably, it's because of difference in result type Option[Something] vs Something, but i thought that it would be the same as this:
for {
a <- Option(1)
....
}
The second question is how to correcly handle errors in (7) to rollback transaction? Do i have to use pattern matching and do something like this:
operation(r) match {
case Left(e) => throw e
}
or i can throw error inside my operation and return Unit instead of Either[Throwable, Unit]?
Also, i have question about (8) and (9). Is it a correct way to start actual processing and handle any error or not?
I tried to do the same steps using this approach:
select() match {
case Some(_) =>
.....
operation(r) match {
case Left(e) => throw e
case Right(_) => ....
}
case None => ....
}
But in result i got too deep match-case clauses and it was hard to read and understand.
I'm new to FP, but i want to implement this in FP way.
scala functional-programming scala-cats scalikejdbc
asked Nov 20 '18 at 10:07
Nick Ryan
376213
Currently, my goal is to communicate with DB using CRUD approach. Between simple operation i may have some extra steps (additional business-logic which may throw some errors).
import cats.effect.IO
import scalikejdbc._
IO(NamedDB(MyDB) localTx {
implicit session => {
val x = for {
a <- IO(select()) // Option[Something] (1)
_ <- IO(log(a)) // Option[Something] (2)
_ <- IO(insert()) // Something (3)
_ <- IO(insert()) // Something (4)
c <- IO(select()) // Option[Something] (5)
r <- IO(fileSystemOperation(a, c)) // (6)
_ <- operation(r) // Either[Throwable, Unit] (7)
} yield ()
x.unsafeRunSync() // (8)
}
}).attempt.unsafeRunSync() match { // (9)
case Left(value) => println("Error")
case Right(value) => println("Success") // in reality i want to return some result here
}
The first problem comes in (2): i got error:
Error type mismatch; found : cats.effect.IO[Unit]
required: Option[?]
_ <- IO(log(a))
But if i log result of any insert ((3) or (4)) then all is ok. Probably, it's because of difference in result type Option[Something] vs Something, but i thought that it would be the same as this:
for {
a <- Option(1)
....
}
The second question is how to correcly handle errors in (7) to rollback transaction? Do i have to use pattern matching and do something like this:
operation(r) match {
case Left(e) => throw e
}
or i can throw error inside my operation and return Unit instead of Either[Throwable, Unit]?
Also, i have question about (8) and (9). Is it a correct way to start actual processing and handle any error or not?
I tried to do the same steps using this approach:
select() match {
case Some(_) =>
.....
operation(r) match {
case Left(e) => throw e
case Right(_) => ....
}
case None => ....
}
But in result i got too deep match-case clauses and it was hard to read and understand.
I'm new to FP, but i want to implement this in FP way.
scala functional-programming scala-cats scalikejdbc
scala functional-programming scala-cats scalikejdbc
asked Nov 20 '18 at 10:07
Nick Ryan
376213
asked Nov 20 '18 at 10:07
Nick Ryan
376213
asked Nov 20 '18 at 10:07
Nick Ryan
376213
asked Nov 20 '18 at 10:07
Nick Ryan
376213
asked Nov 20 '18 at 10:07
Nick Ryan
376213
376213
Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
1
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42
|
show 1 more comment
Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
1
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42
Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
1
1
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42
|
show 1 more comment
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Could you create a Minimal, Complete, and Verifiable example of your problem?
– Yuval Itzchakov
Nov 20 '18 at 11:10
@YuvalItzchakov ok, i'll add runnable example
– Nick Ryan
Nov 20 '18 at 11:14
I think you have several question. It might be good to break them into separate questions on this site, too. You're more likely to get responses to small, constrained questions.
– erip
Nov 20 '18 at 12:17
@erip, yes, probably, you are right. I will decompose this question into severla smaller
– Nick Ryan
Nov 20 '18 at 12:29
1
I'm not sure if you have flexibility in switching around tools, but people really like doobie for JDBC programming. You might find it useful and compositional.
– erip
Nov 20 '18 at 13:42