How to create a more complex aggregate with more than one entity

[Heucles]

Can you put together a sample of what it would look like an aggregate with more than one entity, something like:

• Car (root)

  • Wheel
  • Tire
  • Engine (root of its own aggregate)

• Customer (root)

  • Car (root of its own aggregate)
  • Address

I am having some trouble setting this up, since Customer events can have an effect over the Car aggregate. Can you point me into the right direction?

[adrai]

Hi @Heucles!

An aggregate:

• handles commands and emit events
• ensures the validity of invariants
• is the transactional boundary
• runs business processes
• makes decisions
• focus on verbs (doing) => intention

I would recommend not to start with the entities, start with the intention. Which commands should be sent to the same aggregate to ensures the validity of invariants?

Little hint: Try first to not give your aggregate a name. (first catch intention, then give a name)

If you want, you can even try to do an event storming (by @ziobrando) => https://techbeacon.com/introduction-event-storming-easy-way-achieve-domain-driven-design ;-)