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module ActiveRecord
# Declare an enum attribute where the values map to integers in the database, but can be queried by name. Example:
#
# class Conversation < ActiveRecord::Base
# enum status: [:active, :archived]
#
# # same but with explicit mapping
# enum status: {active: 0, archived: 1}
# end
#
# Conversation::STATUS # => { active: 0, archived: 1 }
#
# # conversation.update! status: 0
# conversation.active!
# conversation.active? # => true
# conversation.status # => :active
#
# # conversation.update! status: 1
# conversation.archived!
# conversation.archived? # => true
# conversation.status # => :archived
#
# # conversation.update! status: 1
# conversation.status = :archived
#
# You can set the default value from the database declaration, like:
#
# create_table :conversations do |t|
# t.column :status, :integer, default: 0
# end
#
# Good practice is to let the first declared status be the default.
module Enum
def enum(definitions)
definitions.each do |name, values|
const_name = name.to_s.upcase
# DIRECTION = { }
const_set const_name, {}
# def direction=(value) self[:direction] = DIRECTION[value] end
class_eval "def #{name}=(value) self[:#{name}] = #{const_name}[value] end"
# def direction() DIRECTION.key self[:direction] end
class_eval "def #{name}() #{const_name}.key self[:#{name}] end"
pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
pairs.each do |value, i|
# DIRECTION[:incoming] = 0
const_get(const_name)[value] = i
# scope :incoming, -> { where direction: 0 }
scope value, -> { where name => i }
# def incoming?() direction == 0 end
class_eval "def #{value}?() self[:#{name}] == #{i} end"
# def incoming! update! direction: :incoming end
class_eval "def #{value}!() update! #{name}: :#{value} end"
end
end
end
end
end
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