Scala + MongoDB: optional fields and immutables

Question

I have this domain object:

case class Person (
  name : String,
  age: Option[Int],
  email : String
) extends MongoObject

with the age optional field. So I defined my factory:

object Person extends MongoObjectShape[Person] {
  lazy val name = Field.scalar("name", _.name)
  lazy val age = Field.optional("age", t => t.age)
  lazy val email = Field.scalar("email", _.email)

  override lazy val * = name :: age :: email :: Nil
  override def factory(dbo: DBObject): Option[Person] = 
    for {
      n <- name from dbo
      t <- age from dbo
      z <- email from dbo
    } yield new Person(n, t, z)
}

but it does not compile, since I get:

[error]  found   : Int
[error]  required: Option[Int]
[error]     } yield new Person(n, t, z)
[error]                           ^

What is wrong with this?

score 4 · Accepted Answer · edited Dec 17 '10 at 18:30

4

maybe, you could write

override def factory(dbo: DBObject): Option[Person] = 
    for {
      n <- name from dbo
      z <- email from dbo
    } yield new Person(n, age from dbo, z)

edited Dec 17 '10 at 18:30

onof

17,167
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answered Dec 17 '10 at 16:54

theRealCisse

56
1

thank you, it works. Definitely I have to learn more about pattern matching in Scala. – onof Dec 17 '10 at 18:32

score 3 · Answer 2 · answered Dec 19 '10 at 17:47

3

A variant of amsayk's answer, but slightly more symmetrical

for {
      n <- name from dbo
      t = age from dbo
      z <- email from dbo
    } yield new Person(n, t, z)

answered Dec 19 '10 at 17:47

Dave Griffith

20,435
3
55
76

score 1 · Answer 3 · answered Dec 17 '10 at 17:15

1

You need to wrap t in a Some object

} yield new Person(n, Some(t), z)

answered Dec 17 '10 at 17:15

Monkey

11
1

that way I will never have the case of None – onof Dec 17 '10 at 18:23
Then what amsayk suggested should work as 'age from dbo' will return an option object. – Monkey Dec 17 '10 at 18:37

Scala + MongoDB: optional fields and immutables

3 Answers3