How could an idiomatic design of Serializable/Cloneable/... look like in Scala?

Question

I wonder how much different these funcionality would look like (and how different the implementation would be), if Scala wouldn't (have to) follow Java's java.io.Serializable/java.lang.Cloneable (mostly to stay compatible with Java and the tools/ecosystem around it).

Because Scala is more simpler in language design, but enables more powerful implementation and abstraction possibilities, it is thinkable that Scala might take a different path compared to Java, if it wouldn't have to shoulder the Java-compatibility-burden.

I could imagine that a idiomatic implementation would use type classes or traits with (possibly) private fields/methods (not possible in Java interfaces?), maybe carrying some standard implementation?

Or are marker interfaces still the right choice in Scala?

Answer 1

Serialization and cloning are both kind of special because of mutability:

• Serialization, because it has to deal with cycles in the object graph, and;
• Cloning because... Well, the only reason to clone an object is to prevent the accidental spread of mutable state.

So, if you're willing to commit to a completely immutable domain model, you don't have object graphs as such anymore, you have object trees instead.

For a functionally-oriented approach to serialization, SBinary is what I'd probably try first. For cloning, Just Don't Do It. :)

Answer 2

Or are marker interfaces still the right choice in Scala?

Nope. They aren't even the right choice in Java. They should be annotations, not interfaces.