It would appear that it is possible to change the implementation of a method on a class with a trait such as follows:
trait Abstract { self: Result =>
override def userRepr = "abstract"
}
abstract class Result {
def userRepr: String = "wtv"
}
case class ValDefResult(name: String) extends Result {
override def userRepr = name
}
val a = new ValDefResult("asd") with Abstract
a.userRepr
Live code is available here: http://www.scalakata.com/52534e2fe4b0b1a1c4daa436
But now I would like to call the previous or super implementation of the function such as follows:
trait Abstract { self: Result =>
override def userRepr = "abstract" + self.userRepr
}
or
trait Abstract { self: Result =>
override def userRepr = "abstract" + super.userRepr
}
However, none of these alternatives compile. Any idea how this could be accomplished?
A subclass can override methods of its superclass, substituting its own implementation of the method for the superclass's implementation.
The trait function can be overridden simply by defining a function with the same name in the class.
Invoking overridden method from sub-class : We can call parent class method in overriding method using super keyword. Overriding and constructor : We can not override constructor as parent and child class can never have constructor with same name(Constructor name must always be same as Class name).
Traits are a useful way of keeping our code DRY (i.e. not repeating ourselves) and sharing methods amongst classes. The fact that we can override and extend the methods from a trait makes them extremely useful!
Here is the answer I was looking for. Thank you Shadowlands for pointing me in the right direction with Scala's abstract override
feature.
trait Abstract extends Result {
abstract override def userRepr = "abstract " + super.userRepr
}
abstract class Result {
def userRepr: String = "wtv"
}
case class ValDefResult(name: String) extends Result {
override def userRepr = name
}
val a = new ValDefResult("asd") with Abstract
a.userRepr
Live code is available here: http://www.scalakata.com/52536cc2e4b0b1a1c4daa4a4
Sorry for the confusing example code, I am writing a library that deals with the Scala AST and was not inspired enough to change the names.
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