[garethjrowlands]

Quite so. I was just trying to make some small suggestions on how to handle the consequences of making that object immutable.

Here are some links along the same lines:

* _Aggregate Roots_ in DDD limit pointers, https://martinfowler.com/bliki/DDD_Aggregate.html * Guidance on where to mutate, _Functional core, imperative shell_, https://www.destroyallsoftware.com/screencasts/catalog/funct...

> using immutable object doesn't make all your problems go away, it makes them different

Yes, and here is a concrete example of the kind of 'different' problems you get: nested immutable structures, say `a.b.c.d`, become harder to update than simply `a.b.c.d = newValue`. The functional solution for this is 'lenses' (and other 'optics'). My favourite Kotlin framework that I use in my day job provides lenses for HTTP - URL query parameters, request and response bodies and so on - which work very well.