Greg Young - CQRS and Event Sourcing - Code on the Beach 2014

https://www.youtube.com/watch?v=JHGkaShoyNs

Notes:

test without getters: 3:28:20 / 6:31:00

don't care about state

if I call 'Deactivate' twice, I get an exception

that's the invariant

VERSIONING

Event Versioning: 4:24:22 / 6:31:00

• add both methods in aggregate

• upcasting old to new event

When do we need to versionize events?

-> when they were written to production

dev? just throw away your local event log

Command Versioning: 4:35:10 / 6:31:00

why? backward compatibility for older clients

eg. we'll keep this for 2 months so clients can upgrade in that time

Snapshot versioning

You can always go from one version to the following or back

otherwise you have a new event