Side Effects

[eballeste]

When reading about custom transition classes to handle side effects there is a note that says the following:

Note: be careful not to have too many side effects within a transition. If you're injecting many dependencies, it's probably a sign that you should refactor your code and use an event-based system to handle complex side effects.

I have several questions (laravel noob)

• Is this only the case when using dependency injection in transition classes?
• What are the pitfalls of using too many custom transition classes for the side effects?
• How can you tell when you have too many?
• What are some examples of an event-based system? Is this some type of pattern? Is it meant to replace the state machine pattern or work together with it?

[brendt]

Is this only the case when using dependency injection in transition classes?

It's usually a good indicator, since many dependencies mean many things happen within that class.

What are the pitfalls of using too many custom transition classes for the side effects?
How can you tell when you have too many?

I can't say anything to the amount of transaction classes. If your business requires many transactions then you can't prevent that

What are some examples of an event-based system? Is this some type of pattern? Is it meant to replace the state machine pattern or work together with it?

I was thinking about event sourcing and using aggregate roots as standalone state machines. I can't go into more detail here. I'm actually creating a course on the topic (https://event-sourcing-laravel.com/) and there's lots of great reading material online.