Inject a dependency inside an object - scala

Question

I'm new to the Play framework and scala and I'm trying to inject a dependency inside a companion object.
I have a simple case class, like:
case class Bar(foo: Int) {}
With a companion object like:
object Bar {
val myDependency =
if (isTest) {
// Mock
}
else
{
// Actual implementation
}
val form = Form(mapping(
"foo" -> number(0, 100).verifying(foo => myDependency.validate(foo)),
)(Bar.apply)(Bar.unapply))
}
This works fine, but it's not really a clean way to do it. I'd like to be able to inject the dependency at build time so that I can inject different mock objects when testing and different real implementations in development and production.
What's the best way to achieve this?
Any help really appreciated. Thanks!

Answer 1

Along the lines of the Cake, we can try to change your example to
trait Validator {
def validate(foo: Int): Boolean
}
trait TestValidation {
val validator = new Validator {
def validate(foo: Int): Boolean = ...
}
}
trait ImplValidation {
val validator = new Validator {
def validate(foo: Int): Boolean = ...
}
}
trait BarBehavior {
def validator: Validator
val form = Form(mapping(...))(Bar.apply)(Bar.unapply)
}
//use this in your tests
object TestBar extends BarBehavior with TestValidation
//use this in production
object ImplBar extends BarBehavior with ImplValidation
You should additionally try and test if this example fits well within the Play Framework, too