Function with Future return type always returns None - scala

Question

I have the following functions:
//retrieves record from database
def getAll: Future[List[User]] = {
try {
Logger.info("Getting all user record.")
db.run(userTableQuery.to[List].result)
}
catch {
case ex: Exception => Logger.error("Exception in getting all user record. " + ex)
Future {
List[User]()
}
}
}
//checks whethe the email exist in list or not
def checkEmail(email : String): Future[Option[User]] ={
/* userRepo.getAll.map(userList => userList.filter(user => user.email == email).map { value => println(value)
userList
})*/
userRepo.getAll.map(userList => userList.filter(user => user.email == email).headOption)
}
//allows to sign in and redirects to dashboard
def signIn() = {
Logger.debug("signingIn in progress. ")
loginForm.bindFromRequest.fold(
formWithErrors => {
Logger.error("Sign-In badRequest.")
Future(BadRequest(views.html.home(webJarAssets, formWithErrors, signUpForm)))
},
validData => {
userService.checkEmail(validData.email).map(value => {
value match {
case Some(us) =>Redirect(routes.HomeController.homePage).flashing("ERROR" -> "User exist")
case None => Redirect(routes.HomeController.homePage).flashing("ERROR" -> "User doesn't exist")
}
}
)
}
)
}
But when I call signin() it always returns None.
I used some debugger code and I guess filter() inside checkMail() is not working properly.
However getall() working properly and gives all the record in database.

Answer 1

I think the problem is in how you compare the user email with the provided one inside the filter in the checkMail() function.
Strings equality is a bit tricky, if you compare them using == you are comparing the objects and not the values so you should use .equals() to compare the values.
You can read more on this blog post
Try to rewrite checkMail() like this:
def checkEmail(email : String): Future[Option[User]] ={
userRepo.getAll.map(userList => userList.filter(user => user.email.equals( email ) ).headOption)
}
You can also simplify .filter() e .headOption using find(), it does the same thing only in one command. You can rewrite it like this:
def checkEmail(email : String): Future[Option[User]] ={
userRepo.getAll.map(userList => userList.find(user => user.email.equals( email ) ) )
}

Answer 2

Instead of using filter you may use find method under checkmail. And also, since this is scala you are using "==" correctly, please see blog here
I hope this code would fix:
//checks whethe the email exist in list or not
def checkEmail(email : String): Future[Option[User]] ={
/* userRepo.getAll.map(userList => userList.filter(user => user.email == email).map { value => println(value)
userList
})*/
userRepo.getAll.map(userList => userList.find(user => user.email == email))
}
I tried to simulate/experiment regarding your implementation in direct way using the terminal:
scala> case class User(email: String)
defined class User
scala> import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.ExecutionContext.Implicits.global
scala> val allUser = scala.concurrent.Future {List(User("carl#test.com"), User("los#test.com"), User("pos#test.com"))}
allUser: scala.concurrent.Future[List[User]] = scala.concurrent.impl.Promise$DefaultPromise#751d3241
scala> val checkmail = allUser.map(userlist=>userlist.find(user=>user.email == "carl#test.com"))
checkmail: scala.concurrent.Future[Option[User]] = scala.concurrent.impl.Promise$DefaultPromise#1358b28e
scala> val rslt = checkmail.map(value => value match {case Some(x) =>println(x); x.email case None => println("None"); "nothing" })
rslt: scala.concurrent.Future[Unit] = scala.concurrent.impl.Promise$DefaultPromise#18324f97
User(carl#test.com)
scala> import scala.concurrent.duration._
import scala.concurrent.duration._
scala> import scala.concurrent._
import scala.concurrent._
scala> Await.result(rslt, 3 seconds)
warning: there was one feature warning; re-run with -feature for details
res8: String = carl#test.com