How to Use Enum in Rails Model in Ruby on Rails

In Ruby on Rails, use enum in your model to map integer values to human-readable symbols. Define it inside the model with a hash or array, like enum status: { active: 0, archived: 1 }, which lets you use methods like user.active? or User.archived.

Syntax

The enum method in a Rails model defines a set of named values mapped to integers stored in the database. It takes a hash or array where keys are names and values are integers. Rails then creates helper methods for querying and setting these values.

• Model attribute: The database column storing the integer.
• Enum definition: Maps names to integers.
• Generated methods: Query scopes, predicate methods, and setters.

ruby

class YourModel < ApplicationRecord
  enum attribute_name: { name1: 0, name2: 1, name3: 2 }
end

Example

This example shows a Task model with a status enum. It stores status as integers but lets you use readable names like :pending or :completed. You can query tasks by status or check a task's status with simple methods.

ruby

class Task < ApplicationRecord
  enum status: { pending: 0, in_progress: 1, completed: 2 }
end

# Usage examples:
task = Task.new

# Set status
 task.status = :pending

# Check status
puts task.pending? # true

# Query all completed tasks
completed_tasks = Task.completed

Output

true

Common Pitfalls

Common mistakes when using enums in Rails include:

• Not having the database column as an integer type.
• Changing enum values order or numbers after data is saved, which breaks existing records.
• Using strings instead of symbols when setting or querying enum values.
• Not handling invalid enum values, which can cause errors.

Always keep enum mappings stable and use symbols for clarity.

ruby

class User < ApplicationRecord
  # Wrong: Using string keys without symbols
  enum role: { 'admin' => 0, 'user' => 1 }

  # Right:
  enum role: { admin: 0, user: 1 }
end

Quick Reference

Feature	Description	Example
Define enum	Map names to integers in model	enum status: { active: 0, archived: 1 }
Set value	Assign enum using symbol	user.status = :active
Check value	Predicate method returns boolean	user.active? # true or false
Query scope	Get all records with enum value	User.archived
Database column	Must be integer type	t.integer :status

Key Takeaways

Use enum in Rails models to map integers to meaningful names for cleaner code.

Always define the enum with symbols and keep the integer mappings stable to avoid data issues.

Rails auto-generates helpful methods like predicates and scopes for easy querying and checks.

Ensure the database column backing the enum is an integer type.

Use symbols when setting or checking enum values to prevent errors.