I'm currently learning Scala and I have some problems designing my case classes. I need two case classes that have the same properties. So I thought I would be a good idea to inherit from an abstract base class that defines these properties. However this code does not compile
abstract class Resource(val uri : String)
case class File(uri : String) extends Resource(uri)
case class Folder(uri : String) extends Resource(uri)
because uri in the case class constructors would overwrite the uri property of the base class.
What would be the correct way to design this?
I want to be able to do something like this
val arr = Array[Resource](File("test"), Folder("test2"))
arr.foreach { r : Resource => r match {
case f : File => println("It's a file")
case f : Folder => println("It's a folder")
} }
The "equivalent" Java code should be something like
abstract class Resource {
private String uri;
public Resource(String uri) {
this.uri = uri
}
public String getUri() {
return uri;
}
}
// same for Folder
class File extends Resource {
public File(String uri) {
super(uri);
}
}
2 Answers
The correct syntax should be:
abstract class Resource {
val uri: String
}
case class File(uri : String) extends Resource
case class Folder(uri : String) extends Resource
Stream[Resource](File("test"), Folder("test2")) foreach {
r : Resource => r match {
case f : File => println("It's a file")
case f : Folder => println("It's a folder")
} }
EDIT
Without case classes:
abstract class Resource(val uri : String)
class File(uri : String) extends Resource(uri) {
override def toString = "..."
}
object File {
def apply(uri: String) = new File(uri)
}
class Folder(uri : String) extends Resource(uri) {
override def toString = "..."
}
object Folder {
def apply(uri: String) = new Folder(uri)
}
Make these two case class extends a common trait which define it interface and it should work.
BTW, you need an identifier before the type clause in case statement.
trait Resource {
val uri: String
}
case class File(uri : String) extends Resource
case class Folder(uri : String) extends Resource
val arr = Array[Resource](File("test"), Folder("test2"))
arr.foreach { r : Resource => r match {
case s: File => println("It's a file")
case s: Folder => println("It's a folder")
}}
