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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 ]
# 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.
#
# Finally, it's also possible to explicitly map the relation between attribute and database integer:
#
# class Conversation < ActiveRecord::Base
# enum status: { active: 0, archived: 1 }
# end
module Enum
def enum(definitions)
klass = self
definitions.each do |name, values|
enum_values = {}
name = name.to_sym
_enum_methods_module.module_eval do
# def direction=(value) self[:direction] = DIRECTION[value] end
define_method("#{name}=") { |value|
value = value.to_s
unless enum_values.has_key?(value)
raise ArgumentError, "'#{value}' is not a valid #{name}"
end
self[name] = enum_values[value]
}
# def direction() DIRECTION.key self[:direction] end
define_method(name) { enum_values.key self[name] }
pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
pairs.each do |value, i|
enum_values[value.to_s] = i
# scope :incoming, -> { where direction: 0 }
klass.scope value, -> { klass.where name => i }
# def incoming?() direction == 0 end
define_method("#{value}?") { self[name] == i }
# def incoming! update! direction: :incoming end
define_method("#{value}!") { update! name => value.to_sym }
end
end
end
end
def _enum_methods_module
@_enum_methods_module ||= begin
mod = Module.new
include mod
mod
end
end
end
end
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