Using Scopes and Custom Queries with Enums #

Rails automatically generates scopes for querying enums, but in advanced scenarios, you might need custom queries to refine results.

1. Default Enum Scopes (Generated by Rails) #

As discussed in earlier chapters, Rails automatically creates scopes for enums:

class User < ApplicationRecord
  enum :status, { active: 0, inactive: 1, banned: 2 }
end

You can use these scopes to filter users:

User.active   # Fetch all active users
User.banned   # Fetch all banned users

However, these default scopes might not be enough in complex applications.

2. Creating Custom Enum Scopes #

Sometimes, we need custom scopes that combine multiple enum values or include additional logic.

Example: Finding all non-banned users

class User < ApplicationRecord
  enum :status, { active: 0, inactive: 1, banned: 2 }

  scope :non_banned, -> { where.not(status: :banned) }
end

Now, you can easily fetch all users who are not banned:

User.non_banned

Example: Combining Multiple Enum Scopes

Let’s say we want to fetch both active and inactive users together.

class User < ApplicationRecord
  enum :status, { active: 0, inactive: 1, banned: 2 }

  scope :active_or_inactive, -> { where(status: [:active, :inactive]) }
end

Now, calling:

User.active_or_inactive

will return all users except banned ones.

3. Using Enums in Raw SQL Queries #

If you’re working with raw SQL, you need to query using integer values.

User.where("status = ?", User.statuses[:active])

This ensures compatibility with Rails enums while using raw SQL.