Is it possible to make an if statement in a for block?
I have the following:
val process = for {
stepIds <- processTemplateDTO.getProcessStepTemplateIds(processTemplateId)
allApprovedProcessTemplates <- processTemplateDTO.getApprovedProcessTemplates(clientId) //Get all approved process templates
processTemplate <- processTemplateDTO.getProcessTemplate(processTemplateId, clientId) // Get the Process Template
prerequisites <- getProcessTemplateForEdit(processPrerequisitesDTO.getProcessPrerequisiteProcessTemplateIdsByProcessTemplateId(processTemplateId), clientId)
postConditions <- getProcessTemplateForEdit(processPostConditionsDTO.getProcessPostConditionProcessTemplateIdsByProcessTemplateId(processTemplateId), clientId)
approvedProcessTemplate <- processTemplateDTO.getProcessTemplate(processTemplate.get.approveprocess, clientId)
if (processTemplate.get.trainingsprocess.isDefined) {
trainedProcessTemplate <- processTemplateDTO.getProcessTemplate(processTemplate.get.trainingsprocess.get, clientId)
}
And I only want to call the processTemplateDTO.getProcessTemplate if processTemplate.get.trainingsprocess.isDefined is true
is this possible?
Thanks
also tried this way:
trainedProcessTemplate <- {
if (processTemplate.get.trainingsprocess.isDefined) {
processTemplateDTO.getProcessTemplate(processTemplate.get.trainingsprocess.get, clientId)
} else {
None
}
}
UPDATE
trainedProcessTemplate <- Nil
_ = if (processTemplate.get.trainingsprocess.get != null) {
processTemplateDTO.getProcessTemplate(processTemplate.get.trainingsprocess.get, clientId)
}
Yes, It is possible.
You can see the below code for reference -
val list = List(1,2,3,4)
val result = for {
id <- list
_ = if (id < 2) {
println(s"Hello I am $id")
}
} yield id
Yes it is possible to use if block in for block, there are two ways
for {
a <- somework1 // returns boolean
b <- somework2 if(a)
} yield (a, b) //anything you like
or you can try
for {
a <- somework1 // returns boolean
b <- if(a) somework2 else somework3
} yield (a, b) //anything you like
In 2nd way you have to give else block as well because without that it will return Any
Hope this helps!
Related
I need to get an entire case class, built with 3 other case classes, back in one call. However, depending on a users credentials they may or may not have access to certain parts of that case class.
Below is how I'm currently doing it.(and it works) It's making the call but clearing out the unauthorized case classes afterwards. I would ideally like to stop the call (due to low bandwidth) if they don't have the proper credentials and return None.
The persistent entity service call is expecting an Option[PersonOne] and Option[PersonTwo] so the .ask must return that or it says it's returning an object and won't compile.
override def getPerson(id: UUID, credOne: Option[Boolean], credTwo: Option[Boolean]) = ServerServiceCall { _ =>
for {
g <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonGeneral)
h <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonOne) //if (credOne) **this 'if' does not work**
s <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonTwo)
} yield {
val x: Option[PersonOne] = if (credOne == Some(true)) h else None
val y: Option[PersonTwo] = if (credTwo == Some(true)) s else None
CompletePerson(g.get, x, y)
//TODO catch if no employee is returned
//throw NotFound (s"Person not Found with $id");
}
}
Here is a version of your function that will only call ask if the appropriate credential value is Some(true):
override def getPerson(id: UUID, credOne: Option[Boolean], credTwo: Option[Boolean]) = ServerServiceCall { _ =>
CompletePerson(
registry.refFor[PersonEntity](id.toString()).ask(GetPersonGeneral).get,
credOne.filter(_ == true).flatMap(_ => registry.refFor[PersonEntity](id.toString()).ask(GetPersonOne)),
credTwo.filter(_ == true).flatMap(_ => registry.refFor[PersonEntity](id.toString()).ask(GetPersonTwo))
)
}
The key part is this:
credX.filter(_ == true).flatMap(...)
If credX is None this will return None
If credX contains false it will return None
If credX is Some(true) then flatMap will call the ask function
If ask returns None then the expression will return None, otherwise it will return Some[PersonX]
I am a bit unclear on some of the data types, but I think this should give you some idea of how to approach this code. (For example, that bare .get look dangerous as it could throw an exception)
Edit after comments
I fixed an issue with the filter(_), it should be filter(_ == true).
It looks like ask actually returns Option[Option[T]], in which case this might be closer to what is needed.
def getPerson(id: UUID, credOne: Option[Boolean], credTwo: Option[Boolean]) = ServerServiceCall { _ =>
for {
g <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonGeneral)
gen <- g
} yield {
val p1 = credOne.filter(_ == true).flatMap(_ => registry.refFor[PersonEntity](id.toString()).ask(GetPersonOne))).flatten
val p2 = credTwo.filter(_ == true).flatMap(_ => registry.refFor[PersonEntity](id.toString()).ask(GetPersonTwo))).flatten
CompletePerson(gen, p1, p2)
}
}
I'm not quite sure what you're asking, but are you concerned that if
registry.refFor[PersonEntity](id.toString()).ask(GetPersonGeneral)
returns None that you'll keep making expensive .ask calls? Cos that won't happen, as we can see from this
def giveMeSome = {println("giving you Some"); Some(1)}
def giveMeNone = {println("giving you None"); None}
def giveMeSomeMore = {println("giving you Some more"); Some(2)}
val ans = for {
a <- giveMeSome
f <- giveMeNone
q <- giveMeSomeMore
} yield (a, f, q)
println(ans)
which prints
giving you Some
giving you None
None
We can also see that in this case, you'll get None back. I can't tell if you want a None or an error thrown. If you want an error, you can just wrap what's above
I didn't get your question completely, but based on my understanding you want to first check if credOne == Some(true) && credTwo == Some(true) then proceed further else return None
override def getPerson(id: UUID, credOne: Option[Boolean], credTwo: Option[Boolean])
=
for {
cone <- credOne
ctwo <- credTwo
if cone
if ctwo
} yield {
ServerServiceCall { _ =>
for {
g <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonGeneral)
h <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonOne)
s <- registry.refFor[PersonEntity](id.toString()).ask(GetPersonTwo)
if g.isDefined
} yield {
CompletePerson(g.get, h, s)
}
}
Given the following Slick code:
val doUpdate = true
val table1 = TableQuery[Table1DB]
val table2 = TableQuery[Table2DB]
val table3 = TableQuery[Table3DB]
val action = (for {
_ <- table1.filter(_.id === id).update(table1Record)
_ <- table2.filter(_.id === id).update(table2Record)
_ <- table3.filter(_.id === id).update(table3Record)
} yield ()).transactionally
What I need is to update table2 and table3 ONLY if the variable doUpdate is true. This is my attempt:
val action = (for {
_ <- table1.filter(_.id === id).update(table1Record)
_ <- table2.filter(_.id === id).update(table2Record)
if (doUpdate == true)
_ <- table3.filter(_.id === id).update(table3Record)
if (doUpdate == true)
} yield ()).transactionally
This compiles, but when I run it I get the following error Action.withFilter failed. How to add the condition?
As you notices if you use if inside a for it will call withFilter underneath. In case of pipelines (DBIO, Futures, Tasks) that filtering boils down to whether or not continue with a pipeline (happy path) or fail it (generating Failure or similar).
If all you want is to update, then you can go with the if road and recover the Future. However, it would we ugly, since depending on how you write the case it might also recover from errors you would like to be informed about.
Alternative is to simply use if-else to provide a different DBIOAction:
(for {
_ <- {
if (doUpdate) conditionalAction.map(_ => ())
else DBIOAction.successful(())
}
} yield ()).transactionally
In your case it could look something like:
val action = (for {
_ <- table1.filter(_.id === id).update(table1Record)
_ <- {
if (doUpdate) DBIOAction.seq(
table2.filter(_.id === id).update(table2Record),
table3.filter(_.id === id).update(table3Record)
)
else DBIOAction.successful(())
}
} yield ()).transactionally
Consider the below code snippet:
In this, I am trying to get values from future using 'For - yield' comprehension. Now in yield method, I need to do a check which makes the call to a function fallbackResult which returns a future and hence return type of getData becomes 'Future[Future[Option[Int]]]' rather than 'Future[Option[Int]]'. How could I make this with a better way? (I did use Map & FlatMap's, but the code little ugly due to nesting Maps and FlatMaps)
def getData(): Future[Future[Option[Int]]] = {
/* These are two future vectors. Ignore the Objects */
val substanceTableF: Future[Vector[OverviewPageTableRowModel]] = getSubstanceTable(substanceIds, propertyId, dataRange)
val mixtureTableF: Future[Vector[OverviewPageTableRowModel]] = getMixtureTableForSubstanceCombination(substanceIds, propertyId, dataRange)
/* I have put for yeild to get values from futures.*/
for {
substanceTable <- substanceTableF
mixtureTable <- mixtureTableF
} yield {
if(substanceTable.isEmpty && mixtureTable.isEmpty) {
val resultF = fallbackResult()
resultF.map(result => {Some(result)})
} else {
Future.successful(Some(100))
}
}
}
private def fallbackResult(): Future[Int] = {
// This method returns future of int
}
There are a lot of ways to handle this, but the key thing is to move your yield logic into your for comprehension. One way to do this is as follows:
for {
substanceTable <- substanceTableF
mixtureTable <- mixtureTableF
result <- (substanceTable.headOption orElse mixtureTable.headOption)
.map(_ => Future.successful(Some(100)))
.getOrElse(fallbackResult)
} yield result
Id put the code inside the for-coprehension:
for {
substanceTable <- substanceTableF
mixtureTable <- mixtureTableF
result <- {
if (substanceTable.isEmpty && mixtureTable.isEmpty)
fallbackResult()
else
Future.successful(Some(100))
}
} yield result
I have a situation similar to below where if request is coming from the UI then request must be validated first before doing anything else. However if request wasn't submitted from the UI - but say via EDI -> in this case there are some biz req how a child data "id" is populated in the request after persisting parent data and use parent data id into child data section. that detail isn't important for this question.
In order to change order of method calls inside a for comprehension I have something similar to below which looks bit repetitive and non idiomatic . is there a better way to achieve this?
def persistData(req : Request) = {
req.actionFromUI match{
case Some(_) => for{
validatedReq <- validateRequest(req) //1st thing
transformedReq <- transformRequest(validatedReq)
persitedReq <- persistRequestData(transformedReq)
}
case None => for{
transformedReq <- transformRequest(validatedReq)
persitedReq <- persistRequestData(transformedReq)
validatedReq <- validateRequest(persitedReq) //last thing
}
}
}
How about something like:
def persistData(req : Request) = {
val (c1, c2, c3) = req.actionFromUI match{
case Some(_) => (validateRequest(req),
transformRequest(validatedReq),
persistRequestData(transformedReq))
case _ => (transformRequest(validatedReq),
persistRequestData(transformedReq),
validateRequest(persitedReq))
}
for {
f1 <- c1
f2 <- c2
f3 <- c3
} // .. do something here with f1, f2, f3
}
Something like this maybe (assuming your validateRequest returns an Option[Request])?
val (preValidate, postValidate) = req.actionFromUI match {
case Some(_) => (validateRequest _, Option[Request].apply _)
case _ => (Option[Request].apply _, validateRequest _)
}
for {
pre <- preValidate(req)
transformed <- transformRequest(pre)
persisted <- persistRequest(transformed)
post <- postValidate(persisted)
}
Or alternatively
def validateRequest(req: Request, pre: Boolean) =
if(req.actionFromUI.isDefined == pre) validateRequest(req) else Some(req)
for {
pre <- validateRequest(req, true)
transformed <- transformRequest(pre)
persisted <- persistRequest(transformed)
post <- validateRequest(persisted, false)
}
In the following scala for loop
private val tpath = for (csvPath <- CsvPaths
if new java.io.File(csvPath).exists()
) yield csvPath
I would like to add a println side effect - similar to the following:
private val tpath = for (csvPath <- CsvPaths
if new java.io.File(csvPath).exists() { // Following is illegal syntax
println(s"Following path exists $csvPath")
}
) yield csvPath
So is there any syntax for adding the side effect to the for/yield loop?
You can use an _ assignment:
for {
csvPath <- CsvPaths
if (new java.io.File(csvPath).exists())
_ = println(s"Following path exists $csvPath")
} yield csvPath
Of course for this specific example you could just use a block for the yield:
for {
csvPath <- CsvPaths
if (new java.io.File(csvPath).exists())
} yield {
println(s"Following path exists $csvPath")
csvPath
}
but the above technique is useful if you want to put calls in the "middle" of a for/yield chain with more <- lines afterwards.
for {
csvPath <- CsvPaths
_ = if(new java.io.File(csvPath).exists()) println(...)
} yield csvPath
or
for {
csvPath <- CsvPaths
} yield {
if(new java.io.File(csvPath).exists()) println(...)
csvPath
}