I want to implement a method which creates a user if it does not exist yet. If it does exist, the user should be returned.
Here's my code:
def createUserIfNotExists(user: User) = {
for {
count <- userService.count(Some(user))
user <- if (count == 0) createUser(user) else userService.findOneByName(user.name)
} yield user
}
My problem is that findOneByName returns Future[Option[User]] and createUser returns Future[User] so the types don't match.
How can I unpack Future[Option[User]] to Future[User] or throw an exception in case there is None?
make createUser also return Future[Option[_]]
def createUserIfNotExists(user: User) = {
for {
count <- userService.count(Some(user))
userOpt <- if (count == 0) createUser(user).map(Some(_)) else userService.findOneByName(user.name)
} yield userOpt
}
or
You can do .get on the option because if count is not zero that means user is definitely available in the database.
def createUserIfNotExists(user: User) = {
for {
count <- userService.count(Some(user))
user <- if (count == 0) createUser(user) else userService.findOneByName(user.name).map(_.get)
} yield user
}
or
First try to retrieve the user if not create the user
def createUserIfNotExists(user: User) = {
for {
userOpt <- userService.findOneByName(user.name)
user <- userOpt match {
case Some(value) => value
case None => createUser(user).map(_ => user)
}
} yield user
}
Note that to ensure correctness in case of parallel database operations it is highly recommended to execute the above code in a transaction
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