What are the disadvantages to declaring Scala case classes?

Question

If you\'re writing code that\'s using lots of beautiful, immutable data structures, case classes appear to be a godsend, giving you all of the following for free with just o

Answer 1

I am quoting this from Scala cookbook by Alvin Alexander chapter 6: objects.

This is one of the many things that I found interesting in this book.

To provide multiple constructors for a case class, it’s important to know what the case class declaration actually does.

case class Person (var name: String)

If you look at the code the Scala compiler generates for the case class example, you’ll see that see it creates two output files, Person$.class and Person.class. If you disassemble Person$.class with the javap command, you’ll see that it contains an apply method, along with many others:

$ javap Person$
Compiled from "Person.scala"
public final class Person$ extends scala.runtime.AbstractFunction1 implements scala.ScalaObject,scala.Serializable{
public static final Person$ MODULE$;
public static {};
public final java.lang.String toString();
public scala.Option unapply(Person);
public Person apply(java.lang.String); // the apply method (returns a Person) public java.lang.Object readResolve();
        public java.lang.Object apply(java.lang.Object);
    }

You can also disassemble Person.class to see what it contains. For a simple class like this, it contains an additional 20 methods; this hidden bloat is one reason some developers don’t like case classes.