We really urge you to think about this yourself first before reading on, because this spoils the exercise. But if you can’t find it, or want to check your answer read on.

Ok, so to answer this challenge, we need to be able answer some things:

What is a played quiz?

According to the domain, a quiz results in a Game Was Opened and that results in either Game Was Started or Game Was Finished. So a played quiz means we have to look at either Game Was Started or Game Was Finished.

How do we find the quiz name?

To do this, we need to create a lookup from gameId to quizId to quizTitle. The domain query is: “what is the title for this game?”.

To create the lookup we can follow this chain. A Game Was Started has a gameId, Game Was Opened has a gameId and a quizId and Quiz Was Created has a quizId and quizTitle.

As was stated earlier, the events are ordered, so if you have a gameId, you know that the quiz was already published.