Command Query Separation (CQS) | Code Walks 025

Command Query Separation (CQS) argues that we should separate methods that perform commands from methods that perform queries. In other words, we should separate methods that return values from methods that mutate state.
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[@JohnMcclaned]

Commands can and should return a result. Specifically for when you are not asking a question, but observing the result of the state change. (like errors or new entity ids) status codes even prove this, they implicitly break the hard "cqs" model because a 200 is technically a response and it means something changed and worked.

[@ades3967]

I was having this same battle in my head today (all the edge cases), where you just bite the bullet and make the exception. Your videos are truly amazing.

[@samoniumuziejus]

Its fine you seperate the concerns, but if you need both you inject both, still the software is broken into smaller bits and pieces, which is the goal mostly

[@stuknowlton160]

@chris, your videos are incredible. I am really grateful for all the knowledge you share. I am constantly referencing your videos at work. Your explanations of patterns and principles is second to none. I can't thank you enough & I eagerly await your next oop video. thanks!

[@mithunmanoharmithun]

awesome explaination..!

[@aleksandrsavvopulo4510]

So “public User createUser(arts)” violates this principle?

[@TonyByng]

Not so much a code 'walk' now 😁

[@robersonmendes1260]

I don't know if you already have a video about, but I miss some example of this concept with command classes and something like this. In my recent job, I found these xxxCommand objects and just don't know nothing about, so here I am

[@chrisjust7445]

What are you riding on in these videos? It sounds like an electric bike, but it looks like you're standing.

[@sanjivkumar2462]

Very nice video. Clear explanation of CQS. I was curious where are you located. Place looks beautiful.

[@rajusrinivasan8820]

When you do video driving more interesting then in a room.