Business logic in theory occupies the middle tier of a 3-tier architecture.

Do add business logic to helpers or utilities, so you can test them separately from your component.

These methods should be used with caution, however, because important business rules and application logic may be kept in callbacks. Bypassing them without understanding the potential implications may lead to invalid data.

Provides a bunch of primitives to write declarative business logic

Trailblazer strikes when it comes to organizing business code.

An endpoint links your routing with your business code. The idea is that your controllers are pure HTTP routers, calling the respective endpoint for each action. From there, the endpoint takes over, handles authentication, policies, executing the domain code, interpreting the result, and providing hooks to render a response.

In Trailblazer, models are completely empty. They solely contain associations and finders. No business logic is allowed in models.

Operations encapsulate business logic and are the heart of a Trailblazer architecture.

ActiveInteraction plays nicely with Rails. You can use interactions to handle your business logic instead of models or controllers.

simplify complex business logic

"Headless Tippy" refers to Tippy without any of the default element rendering or CSS. This allows you to create your own element from scratch and use Tippy for its logic only.

We all know that real business logic does not belong in the presentation layer, but what about simple presentation-oriented things like coloring alternate rows in table or marking the selected option in a <select> dropdown? It seems equally wrong to ask the controller/business logic code to compute these down to simple booleans in order to reduce the logic in the presentation template. This route just lead to polluting the business layer code with presentation-oriented logic.