using extended abstract class

You gave the type of the class, not an instance of it

println(new Card(8,new Cards.Club).toXML)

this works

Axel Rose wrote:
>
> Hello,
>
> I'm just learning Scala for fun and while testing things I found this
> example:
>
> ---
> trait XML {
> def toString(): String
> def toXML(): String = ""
> }
>
> object Cards {
> sealed abstract class Suit
> case class Club extends Suit { override def toString() = "Clubs"
> }
> case class Diamond extends Suit { override def toString() = "Diamonds"
> }
> case class Heart extends Suit { override def toString() = "Hearts"
> }
> case class Spade extends Suit { override def toString() = "Spades"
> }
> }
>
> case class Card(value: Int, suit: Cards.Suit) extends XML {
> override def toString() = value + " of " + suit
> }
> ---
>
> When trying to create a new Card instance I get this though:
>
> scala> new Card(8,Cards.Club)
> :9: error: type mismatch;
> found : Cards.Club.type (with underlying type object Cards.Club)
> required: Cards.Suit
> new Card(8,Cards.Club)
>
>
> What is wrong with my example code?
>
>
> Thanks and have a nice holiday time,
> Axel.
>
>

Cards.Club is a function

scala> val x = Cards.Club
x: Cards.Club.type =

Cards.Club() is an instance of suit

scala> val x = Cards.Club()
x: Cards.Club = Clubs

This works Card(23, Cards.Club())

On Sat, Dec 27, 2008 at 9:13 AM, Axel Rose wrote:
> Hello,
>
> I'm just learning Scala for fun and while testing things I found this
> example:
>
> ---
> trait XML {
> def toString(): String
> def toXML(): String = ""
> }
>
> object Cards {
> sealed abstract class Suit
> case class Club extends Suit { override def toString() = "Clubs" }
> case class Diamond extends Suit { override def toString() = "Diamonds" }
> case class Heart extends Suit { override def toString() = "Hearts" }
> case class Spade extends Suit { override def toString() = "Spades" }
> }
>
> case class Card(value: Int, suit: Cards.Suit) extends XML {
> override def toString() = value + " of " + suit
> }
> ---
>
> When trying to create a new Card instance I get this though:
>
> scala> new Card(8,Cards.Club)
> :9: error: type mismatch;
> found : Cards.Club.type (with underlying type object Cards.Club)
> required: Cards.Suit
> new Card(8,Cards.Club)
>
>
> What is wrong with my example code?
>
>
> Thanks and have a nice holiday time,
> Axel.
>

Quoting Axel Rose :

> object Cards {
> sealed abstract class Suit
> case class Club extends Suit { override def toString() = "Clubs" }
> case class Diamond extends Suit { override def toString() = "Diamonds" }
> case class Heart extends Suit { override def toString() = "Hearts" }
> case class Spade extends Suit { override def toString() = "Spades" }
> }

Your best best is actually to just make all these "case object"
instead of "case class", then the rest of your code should work as-is.
Presumably you're making a home-grown enumeration and you'll never
need more than one instance of each Suit.

-0xe1a

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