Generate abstract base classes for entities together with entity states

[alexander-yevsyukov]

We can ease creation of entity classes by generating abstract bases that would take work of specifying generic parameters. For example, for an entity state called NumberStats (which has the kind PROJECTION) it would be like this:

internal abstract class PNumberStats : Projection<Int, NumberStats, NumberStats.Builder>()

This way, the user would be able to start his NumberStatsView or NumberStatsProjection like this:

internal class NumberStatsView : PNumberStats() {
  ...
}

Please note the P prefix of the generated abstract base. It's meant to give the developer information about the kind of the entity.
So, we can have A for Aggregate, and Pm for ProcessManager.

I suggest generating such abstract bases only for Kotlin, assembling them into a file called EntityClassesKt.kt.

internal access

Please note the internal modifier set for the generated abstract base. This way we force the derived class to be internal as well.

Related issues

• [Draft] Named Queries #35

[alexander-yevsyukov]

Instead of having a prefix based on the type of the entity, we can have a common convention which is simpler to remember and understand: suffix form (!) Base. So, in the scenario given in the issue description it would be NumberStatsBase.

Or, which is probably better, assuming we're basing on Kotlin, it could be just a generated typealias!

[alexander-yevsyukov]

It's still not sure if "obfuscating" the generic parameter is such a way is a good idea. Knowing a builder type is a good thing when writing receptor functions. It helps with the Kotlin DSL for builders.