How to use hexagonal architecture in a Rails application

Hexagonal architecture in Rails

In Rails, we can use the following rails components to play the role of port, adapter, and external devices in hexagonal architecture:

• Ports: HTTP protocol and message queue clients
• Adapters: The Rails controllers, HTTP and message queue clients
• External devices: The user interface, databases and infrastructure

Rails controllers

The following core responsibilities make the controllers work like the adapters of the hexagonal architecture:

1. Play the role of the application’s interface to the HTTP protocol.
2. Respond to HTTP messages by triggering actions on a domain objects.
3. Check and query the model objects to find out if they performed their tasks.

1. As discussed above, in Rails, controllers play the role of adapters, so business logic is not contained in the controllers. This makes it easier for controllers to coordinate with external sources. Here, use case service components (service objects) can be used with controllers to separate each business logic and allow controllers to coordinate with external sources.

• Service objects are designed to execute one service at a time, perform it well, and provide a single point of failure. One controller can have multiple services based on the number of business logic actions it wants to perform.

2. Using passive controllers is another way we can implement the hexagonal architecture in Rails. Passive controllers are the controllers that do not make any decision on the use case service failure or success. They only invoke or get invoked on requests or callbacks from the service objects.

3. To not clutter the business logic and controllers with the codebase, calls to database are handled separately. Repositories can be used as a descriptive and easily testable interface for querying the database to perform a single responsibility at a time. Repositories can manage all interactions with the database so interactions with external sources become relatively easy.