Mongoid::Enum

Enum implementation for Mongoid. Similar to that found in ActiveRecord.

Installation

gem "mongoid_enum"

Usage

By default values saved to DB are strings matching enum labels.

class Conversation
  include Mongoid::Document
  include Mongoid::Enum

  enum status: [ :active, :archived ]
end

conversation = Conversation.active.first
conversation.active?   # true
conversation.archived! # immediately saves document
conversation.active?   # false
conversation["status"] # "archived"

You can use other Mongo value types (numbers, booleans, nil) when explicitly defining the enum mapping:

class Part
  include Mongoid::Document
  include Mongoid::Enum

  enum quality_control: {pending: nil, passed: true, failed: false}, _prefix: :qc
end

part = Part.qc_pending.first
part.qc_pending?        # true
part["quality_control"] # nil
part.quality_control    # "pending"
part.qc_passed!
part.quality_control    # "passed"
part["quality_control"] # true

Enum values are validated.

part.quality_control = "unknown value"
part.valid? # false

You can access the mapping as hash with indifferent access via class level constant. Constant name is a pluralized field name set in SCREAMING_SNAKE_CASE.

Part::QUALITY_CONTROLS["passed"] # true
Part::QUALITY_CONTROLS[:failed]  # false

You might prefer to use plural scopes if your field values are nouns:

class Attachment
  include Mongoid::Document
  include Mongoid::Enum

  enum type: %w{image video}, _plural_scopes: true
end

Attachment.videos.count

Read more in documentation.

Differences from ActiveRecord

1. Default values are strings, not integers. I think it fits MongoDB better.

2. Mapping hash is accessible via class constant instead of class method. I prefer constant because it is accessible without prefix both on class methods and instance methods. Also I think SCREAMING_SNAKE_CASE is less likely to cause name conflicts.

3. I do not raise exception when invalid value is assigned. Instead document fails validation. Assigned invalid value is remembered and can be corrected in forms. Exception will still be raised if you try to save invalid label by skipping validation (save validate: false). That's because the document does not know how to convert invalid enum option to database value.

Credits

Original implementation for ActiveRecord was created by David Heinemeier Hansson. Following modifications by other Rails contributors. Port to Mongoid prepared by Adam Wróbel.