Document CQRS

[sarjon]

I referred to PrestaShop/PrestaShop#9370 and found that explanation well written, so I basically ended up copying @eternoendless work with some minor changes to it. 😈

I have a few questions:

1. Should I provide code examples of how to create and use command/handler? Or maybe it should be subsection of CQRS?
2. Is Architecture good section for this article? I was also thinking about Architecture/Migration Guide, but it feels a bit wrong.

[mickaelandrieu]

Nice introduction!

For me the docs should answer some questions of the PrestaShop developers:

• what is CQRS? (your introduction);
• am I concerned by this stuff when working on themes or modules? (tutorials, and/or workflows) Imagine you need to explain that in training for instance;
• what are the pros/cons of this choice for the PrestaShop developers (ie: why we decide to do that and how it helps PrestaShop developers to work with our platform?);

WDYT? /c @eternoendless

[matks]

1. Should I provide code examples of how to create and use command/handler? Or maybe it should be subsection of CQRS?

In another subsection, yes 😉it's 2 subtopics: what is X and how we implement X in PrestaShop. Like "what is Dependency Injection" and "How Symfony implements Dependency Injection with the Symfony Container"

2. Is Architecture good section for this article? I was also thinking about Architecture/Migration Guide, but it feels a bit wrong.

Looks like the right place to me 👍

[matks]

Can you explain why we need to keep core and why we need to isolate it ?
Something like

"We are currently migrating PrestaShop Back Office to Symfony but the new Controllers, Templates and classes dedicated to the BO are still using the Core classes of PrestaShop used by the previous BO. One day, we will remove this Core too. Until that day, we need to allo the new BO to access these classes and data while keeping a clear border between these 2 areas of code as one is expected to remain and the other one to disappear."

[sarjon]

Do you think this commit b908ef4 explains it?

[matks]

It could be nice to have a schema here. This schema would compare old and new architecture.

In old architecture we would see the browser sending HTTP requests to a big bunch of code which would contain Controllers calling directly core classes. Like:

browser ==(send HTTP requests)==> controller ==(calls)==> core

In new architecture, we would show the clear separation of the bus

browser ==(send HTTP requests)==> SF controller =(dispatchs Queries and Commands)=> Bus routing =(Handler handles the Command/Query)=> Adapter Handler ==(calls)==> core

[sarjon]

Interesting, I've tried to do so in b908ef4 commit, could you check?

[matks]

👍

[matks]

Thank you @sarjon