Class and Companion Objects hierarchy

[pedro rijo]

Hey,

I would like to better understand how does class inheritance works when mixing classes and companion objects.

If a class Child extends Parent (possibly with ParentTrait), the Object Child will inherit from Parent (and ParentTrait) also right?

But can Object Child extends other classes/traits? If so, what will be the implications for the Child class, and for the Child companion object?

Thanks,

Pedro Rijo

[Naftoli Gugenheim]

On Wed Feb 25 2015 at 1:30:20 PM pedro rijo <pedro...@gmail.com> wrote:

Hey,

I would like to better understand how does class inheritance works when mixing classes and companion objects.

If a class Child extends Parent (possibly with ParentTrait), the Object Child will inherit from Parent (and ParentTrait) also right?

No.

 

But can Object Child extends other classes/traits? If so, what will be the implications for the Child class, and for the Child companion object?

They are two unrelated types. The object can extend whatever it wants, and the class can extend whatever it wants.

Thanks,

Pedro Rijo

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[pedro rijo]

So what you are saying is that are 2 independent objects, the only diference is that Object can access Class instance private variables?

[Naftoli Gugenheim]

Basically, it could be there are other ramifications that are not coming to mind.

[Oliver Ruebenacker]

     Hello,

  If you have a case class, the compiler will add an apply method to its companion object that takes the same arguments as the primary constructor of the case class, passes them to the primary constructor, and returns the constructed instance. If you did not declare a companion object, the compiler will create one.

  If you access Scala code from Java code, a class and its companion object will look like the same class on the Java side, with the members of the companion object being the static members.

     Best, Oliver 

--

Oliver Ruebenacker

Solutions Architect at Altisource Labs

Be always grateful, but never satisfied.

[pedro rijo]

Thank you all :)

--

Obrigado,

Pedro Rijo

[Naftoli Gugenheim]

On Wed Feb 25 2015 at 4:00:47 PM Naftoli Gugenheim <nafto...@gmail.com> wrote:

Basically, it could be there are other ramifications that are not coming to mind.

Right --- implicit search.

class C

object D {

  implicit val c: C = new C

}

implicitly[C] // compiler error --- but if you rename D to C then it finds it.

 

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