In Slick (Scala), how to refactor codes like this? - scala

Question

I see codes like this:
trait LoginInfoRepoImpl extends LoginInfoRepo {
def loginInfoRepository = new LoginInfoRepository {
private val loginInfoTable = TableQuery[LoginInfoTable]
// return a LoginID
def save(userLoginInfo: userLoginInfo): Future[userLoginID] = Future {
val newRecord = DB.withSession { implicit session =>
loginInfoTable.filter(
l => l.userID === userLoginInfo.userID &&
(l.deviceID === userLoginInfo.deviceID || (l.deviceID.isEmpty && userLoginInfo.userID.isEmpty))).list.headOption.fold {
val newSubID = loginInfoTable.filter(l => l.userID === userLoginInfo.userID).sortBy(_.subID.desc).take(1).map(_.subID).list.headOption.getOrElse(0) + 1
(loginInfoTable returning loginInfoTable) += LoginInfoRecord(userLoginInfo.userID, newSubID, userLoginInfo.deviceID, userLoginInfo.userAgent, getCurrentTime)
} { l =>
// to do : update time
val q = for (l <- loginInfoTable if l.userID === userLoginInfo.userID && ((l.deviceID === userLoginInfo.deviceID)
|| (l.deviceID.isEmpty && userLoginInfo.userID.isEmpty)))
yield l.lastLoginTime
q.updateReturning(loginInfoTable.map(identity), getCurrentTime).head
}
}
userLoginID(newRecord.userID, newRecord.subID.toString)
}
}
}
This looks a little monstrous for me. I found many things are crowded into one line. Also, I found l.deviceID is of type Column[Option[String]], while userLoginInfo.deviceID is of typeOption[String], they don't equal if both of them is None. Thus a l.device.isEmpty looks necessary..
Does anyone have suggestions about how to refactor these codes? Thanks!

Answer 1

First of all: Better indentation and breaking up long lines.
Slick-specific: pull queries out of the withSession block and reuse them for shared logic. Use firstOption instead of .list.headOption.
Side-note: Since you are generating IDs based on old ones, you may want to use a transaction or use a more efficient means provided by your DB.
trait LoginInfoRepoImpl extends LoginInfoRepo {
def loginInfoRepository = new LoginInfoRepository {
private val loginInfoTable = TableQuery[LoginInfoTable]
// return a LoginID
def save(userLoginInfo: userLoginInfo): Future[userLoginID] = Future {
val userLoginInfoQuery = loginInfoTable.filter(l => l.userID === userLoginInfo.userID)
val deviceLoginInfoQuery = userLoginInfoQuery.filter(
l =>
l.deviceID === userLoginInfo.deviceID ||
(
l.deviceID.isEmpty && userLoginInfo.userID.isEmpty
)
)
val subIdQuery = userLoginInfoQuery.sortBy(_.subID.desc).map(_.subID)
val newRecord = DB.withTransaction{ implicit session =>
deviceLoginInfoQuery
.firstOption
.fold {
val newSubID = subIdQuery.firstOption.getOrElse(0) + 1
val newLoginInfo = LoginInfoRecord(userLoginInfo.userID, newSubID, userLoginInfo.deviceID, userLoginInfo.userAgent, getCurrentTime)
(loginInfoTable returning loginInfoTable) += newLoginInfo
}( _ =>
// to do : update time
deviceLoginInfoQuery
.map(_.lastLoginTime)
.updateReturning(loginInfoTable.map(identity), getCurrentTime)
.head
)
}
userLoginID(newRecord.userID, newRecord.subID.toString)
}
}
}