Conditional Routing in Ruby on Rails Using Custom Constraints

In complex Ruby on Rails applications, it’s common to route requests based on dynamic conditions, such as the value of a query parameter. One powerful way to handle such cases is to use custom routing constraints. This article demonstrates how to route the same endpoint to different controllers based on the subject_type parameter.

Problem

Suppose we want to handle updates to details of various animal types—dogs, cats, and mice—through a single endpoint like:

⚠️ Why Including nil in .where(id: [...]) Can Severely Impact PostgreSQL Performance

When writing queries like: