Scala案例类和构造函数

Question

I'm finding myself writing a lot of (sort of) boilerplate code. For example say I have the following traits

trait Foo {
  def x: Int
}

trait Bar {
  def y: Boolean
  def z: String
}

Then I want a case class that does no more or less than implement these.

case class MyClass(x: Int, y: Boolean, z: String) extends Foo with Bar

This doesn't seem annoying, but now imagine that my traits have a dozen def s each and that the names x , y , and z are much longer. Writing the case class out means I have to rewrite all of these as arguments of MyClass .

Is there a way to generate the x: Int, y: Boolean, z: String constructor part automatically based on the traits I extend?

Answer 1

I think what you are looking for is an annotation macro that can handle this work for you. You would then invoke this macro by writing something like this:

@FieldsFromTraits
case class MyClass extends Foo with Bar

Annotation macros can then rewrite your case class with information from the traits.

A library that does something similar is MetaRest . You might try to adapt that implementation. I'll see if I can't put something together tonight.