Q & A Thread #6 – what are your questions for Justin Weiss and Avdi?

[Ross Reinhardt]

We’ve been talking in the course about the kind of messages that you send between objects, and specifically looking at how it can be better so send a message that notifies the other object of an event that occurred like PurchaseLlamas#payment_approved rather than tell it what to do like PurchaseLlamas#complete_transaction to allow for the fact that the underlying implementation may change.

Currently, for example, I’m working on an access control system where you can grant and revoke permissions for a given user and permission. It’s hard for me to think past just a command like AccessControl#grant_permission or AccessControl#revoke_permission and frame as an event. Maybe it could be more like AccessControl#permission_granted and #permission_revoked.

I would love to hear your insights around how you determine what messages objects in your system should send each other. Thanks!

[Andrei Crudu]

Hello Avdi and Justin,

What level of decoupling of business logic from rails do you recommend? At what point do you hit diminishing returns and makes implementing new features very painful.

For example I tried to use Uncle Bob’s methodology of decoupling the business logic from rails and to invert the dependency relation between them. Basically my business logic had no knowledge of rails or anything rails related. It was quite awesome but writing the tests was super painful. Plus building new features was taking a whole lot more time.

Eventually we ditched the 100% separation from rails, and kept most of the stuff. It was a great learning experience, but I am still wondering if there is a better way to achieve 100% separation of the business logic from rails stuff. An easy way.

What I am most interested in is your thoughts about extracting the business logic of an application and separating it from the framework. What is a good way to get started so as to be as productive as possible, while building for the future so as to depend even less on the framework as time goes by. What are the major steps you see to achieving this?

[Andrei Crudu]

When using composition and lots of indirection to model your domain, it can become quite hard to keep track of how all the pieces fit together. What are some tricks and tips to make it more obvious how everything works together so it becomes easy for other developers to pick up and extend existing functionality.

Also, how to best spread the team knowledge about the code base so existing small pieces of functionality get reused instead of writing them again from the ground up. Basically how can I help the other team members see and realize the opportunities to compose their code mostly using pre-existing code widgets when they are available, and writing from scratch only what doesn’t exist.

[Avdi Grimm]

Just a reminder to everyone: @justinweiss is the creator of the Whole Value Objects in Rails lesson, that we had a lot of conversation about. If anyone still has questions about that topic, today would be a great day to ask them

[Andrei Crudu]

Can Whole Value Objects be considered DDD Value Object? Are they the same thing?

[Ross Reinhardt]

Oh wow yes! Whole value objects one question I’ve had recently on that was around how generic/ specific it’s beneficial to make them. For example, in our application right now we have many user supplied titles that we always want to make sure have the whitespace striped from them before they are saved. In a case like that, would a more generic WhitespaceEscaped type whole value object or would it be wiser to have specific objects like LessonTitle for each of the cases that specify their own specific behavior which currently means escaping white space? Or is it even a good idea to handle escaping white space in a whole value object?

[Peter Schmitt]

How much do you use Ruby and/or Rails on new projects versus other languages/frameworks?

[Avdi Grimm]

Thanks all! Be sure to put in your suggestion for the next Q&A guest: https://discuss.avdi.codes/t/who-should-be-the-next-q-a-guest/563