ActiveEnum

Define enum classes in Rails and use them to enumerate ActiveRecord attributes. Brings together some ideas of similar plugins that I liked and does it they way I prefer.

Enum values are stored in memory at the moment but I plan to add database and yaml.

Install

On Gemcutter:

sudo gem install active_enum

And add to your Rails environment.rb

config.gem 'active_enum'

Example

Define an enum class with values

class Sex < ActiveEnum::Base
  value :id => 1, :name => 'Male'
  value :id => 2, :name => 'Female'
end

Define using implicit id values

class Sex < ActiveEnum::Base
  value :name => 'Male'
  value :name => 'Female'
end

Beware that if you change the order of values defined in an enum which don’t have explicit ids, then the ids will change. This could corrupt your data if the enum values have been stored in a model record, as they will no longer map to the original enum.

You can also define the sort order of returned values

class Sex < ActiveEnum::Base
  order :desc

  value :id => 1, :name => 'Male'
  value :id => 2, :name => 'Female'
end

Enum class usage

Sex[1]        # => 'Male'
Sex['Male']   # => 1
Sex[:male]    # => 1
Sex.to_select # => [['Male', 1], ['Female',2]] for select form helpers

Use the enum to enumerate an ActiveRecord model attribute

class User < ActiveRecord::Base
  enumerate :sex, :with => Sex
end

Skip the with option if the enum can be implied from the attribute

class User < ActiveRecord::Base
  enumerate :sex
end

Define enum class implicitly in enumerate block

class User < ActiveRecord::Base
  # defines UserSex enum
  enumerate :sex do
    value :name => 'Male'
  end
end

Multiple attributes with same enum

class Patient < ActiveRecord::Base
  enumerate :to, :from, :with => Sex
end

Access the enum values and the enum class using the attribute method with a symbol for the enum component you want

user = User.new
user.sex = 1
user.sex         # => 1

user.sex(:id)    # => 1
user.sex(:name)  # => 'Male'
user.sex(:enum)  # => Sex

You can check if the attribute value matches a particular enum value by passing the enum value as an argument to the question method

user.sex?(:male)    # => true
user.sex?(:Male)    # => true
user.sex?('Male')   # => true
user.sex?('Female') # => false

A convience method on the class is available to the enum class of any enumerated attribute

User.enum_for(:sex) # => Sex

You can set the default to return the enum name value for enumerated attribute

ActiveEnum.use_name_as_value = true
user.sex # => 'Male'

Define enum classes in bulk without class files, in an initializer file for example.

ActiveEnum.define do

  # defines Sex
  enum(:sex) do
    value :name => 'Male'
    value :name => 'Female'
  end

  # defines Language 
  enum(:language) do
    value :name => 'English'
    value :name => 'German'
  end

end

All defined enum classes are stored in ActiveEnum.enum_classes array if you need look them up or iterate over them.

You can make an existing model class behave like an enum class with acts_as_enum

class User < ActiveRecord::Base
  acts_as_enum :name_column => 'first_name'
end

Giving you the familiar enum methods

User[1]
User['Dave']
User.to_select

TODO

more docs
storage options of memory, database or yaml
use custom method name for the enumerated attribute
named_scopes
question methods for enum names e.g. user.male?
possibly allow string enum values to assigned to attributes
add enum value class for instances if there is a need