Suppose I have a Java class with multiple constructors:
class Base {
Base(int arg1) {...};
Base(String arg2) {...};
Base(double arg3) {...};
}
How can I extend it in Scala and still provide access to all three of Base's constructors? In Scala, a subclass can only call one of it's superclass's constructors. How can I work around this rule?
Assume the Java class is legacy code that I can't change.
It's easy to forget that a trait may extend a class. If you use a trait, you can postpone the decision of which constructor to call, like this:
trait Extended extends Base {
...
}
object Extended {
def apply(arg1: Int) = new Base(arg1) with Extended
def apply(arg2: String) = new Base(arg2) with Extended
def apply(arg3: Double) = new Base(arg3) with Extended
}
Traits may not themselves have constructor parameters, but you can work around that by using abstract members instead.