Not enough arguments for constructor although I use the Option[] Type

Question

I'm new to scala and I have a very simple problem :

I defined a class like this :

case class Image (imageId: Long, userId: Option[Long])

But if I want to create an instance of this class with only an imageId like this :

var newImage = new Image(1)

I get this error although I'm using an Option[Long] :

not enough arguments for constructor 
Unspecified value parameter userId.

What I am doing wrong? Thanks ;)

Answer 1

To reiterate the error message you're not giving it enough arguments. Option is not optional in that you have to provide a value for it namely Some or None. If you don't want to provide a value and want to use a default value you can give one in the constructor like so:

case class Image(imageId, Long, userId: Option[Long] = None)

Then you can do this and the default value None is used.

scala> var newImage = new Image(1)
newImage: Image = Image(1,None)

Of course, you can still provide a value when you have one.

scala> var newImage = new Image(1, Some(42))
newImage: Image = Image(1,Some(42))