attr_enumerator¶ ↑

A method for restricting an attribute to a set of choices.

An invocation of attr_enumerator will create:

• a class constant containing all valid choices

• a validation requiring the attribute’s value to be one of the choices

• instance methods for each choice, returning true if the attribute is that value and false otherwise

• scopes for each choice that retrieve records where the attribute is that value

class Car < ActiveRecord::Base
  attr_enumerator :color, ['red', 'blue']
end

# constant
Car::COLORS           # => ['red', 'blue']

# validation
car = Car.new
car.color = 'green'
car.valid?            # => false
car.errors            # => {:color => ["is invalid"]}
car.color = 'red'
car.valid?            # => true

# instance methods
car.red?              # => true
car.blue?             # => false

# scopes
car.save
Car.red               # => [<#Car>]

The AttrEnumerator module will be automatically included in ActiveRecord::Base, making the attr_enumerator method available in all ActiveRecord models.

To include AttrEnumerator on a non-ActiveRecord model the class must also include ActiveModel::Validations and provide an accessor to the attribute. The model will have all the above functionality except no scopes will be generated.

class Car
  include ActiveModel::Validations
  include AttrEnumerator

  attr_accessor :color
  attr_enumerator :color, ['red', 'blue']
end

Options may be passed as the last argument to attr_enumerator to configure its behavior. For example:

class Car < ActiveRecord::Base
  attr_enumerator :color, ['red', 'blue'], :constant => :PAINT_COLORS, :prefix => :painted
end

Car::PAINT_COLORS   # => ['red', 'blue']

car = Car.new
car.color = 'red'
car.painted_red?    # => true

• constant (default: pluralized, uppercased attribute name)

  Set a custom constant name.

• prefix (default: nil)

  Set a prefix for generated methods and scopes.

• message (default: internationalized "is invalid")

  Set the validation error message when the attribute is not a valid value. Use %{value} to refer to the value of the attribute, e.g. "%{value} is not a valid choice".

• allow_nil / allow_blank (default: false)

  Do not fail validation when the attribute is nil or blank.

• if / unless (default: unused)

  Set a method, proc or string to call to determine if the validation should occur. See ActiveModel::Validations for more details.

• Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet

• Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it

• Fork the project

• Start a feature/bugfix branch

• Commit and push until you are happy with your contribution

• Make sure to add tests for it. This is important so I don’t break it in a future version unintentionally.

• Create a pull request

• Let me know if you want to be included in CONTRIBUTORS.txt