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require 'active_support/core_ext/object/deep_dup'
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.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"
#
# # conversation.update! status: nil
# conversation.status = nil
# conversation.status.nil? # => true
# conversation.status # => nil
#
# Scopes based on the allowed values of the enum field will be provided
# as well. With the above example:
#
# Conversation.active
# Conversation.archived
#
# Of course, you can also query them directly if the scopes don't fit your
# needs:
#
# Conversation.where(status: [:active, :archived])
# Conversation.where.not(status: :active)
#
# 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 with a +Hash+:
#
# class Conversation < ActiveRecord::Base
# enum status: { active: 0, archived: 1 }
# end
#
# Note that when an +Array+ is used, the implicit mapping from the values to database
# integers is derived from the order the values appear in the array. In the example,
# <tt>:active</tt> is mapped to +0+ as it's the first element, and <tt>:archived</tt>
# is mapped to +1+. In general, the +i+-th element is mapped to <tt>i-1</tt> in the
# database.
#
# Therefore, once a value is added to the enum array, its position in the array must
# be maintained, and new values should only be added to the end of the array. To
# remove unused values, the explicit +Hash+ syntax should be used.
#
# In rare circumstances you might need to access the mapping directly.
# The mappings are exposed through a class method with the pluralized attribute
# name, which return the mapping in a +HashWithIndifferentAccess+:
#
# Conversation.statuses[:active] # => 0
# Conversation.statuses["archived"] # => 1
#
# Use that class method when you need to know the ordinal value of an enum.
# For example, you can use that when manually building SQL strings:
#
# Conversation.where("status <> ?", Conversation.statuses[:archived])
#
module Enum
def self.extended(base) # :nodoc:
base.class_attribute(:defined_enums)
base.defined_enums = {}
end
def inherited(base) # :nodoc:
base.defined_enums = defined_enums.deep_dup
super
end
class EnumType < Type::Value
def initialize(name, mapping)
@name = name
@mapping = mapping
end
def cast(value)
return if value.blank?
if mapping.has_key?(value)
value.to_s
elsif mapping.has_value?(value)
mapping.key(value)
else
raise ArgumentError, "'#{value}' is not a valid #{name}"
end
end
def deserialize(value)
return if value.nil?
mapping.key(value.to_i)
end
def serialize(value)
mapping.fetch(value, value)
end
protected
attr_reader :name, :mapping
end
def enum(definitions)
klass = self
definitions.each do |name, values|
# statuses = { }
enum_values = ActiveSupport::HashWithIndifferentAccess.new
name = name.to_sym
# def self.statuses statuses end
detect_enum_conflict!(name, name.to_s.pluralize, true)
klass.singleton_class.send(:define_method, name.to_s.pluralize) { enum_values }
detect_enum_conflict!(name, name)
detect_enum_conflict!(name, "#{name}=")
attribute name, EnumType.new(name, enum_values)
_enum_methods_module.module_eval do
pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
pairs.each do |value, i|
enum_values[value] = i
# def active?() status == 0 end
klass.send(:detect_enum_conflict!, name, "#{value}?")
define_method("#{value}?") { self[name] == value.to_s }
# def active!() update! status: :active end
klass.send(:detect_enum_conflict!, name, "#{value}!")
define_method("#{value}!") { update! name => value }
# scope :active, -> { where status: 0 }
klass.send(:detect_enum_conflict!, name, value, true)
klass.scope value, -> { klass.where name => value }
end
end
defined_enums[name.to_s] = enum_values
end
end
private
def _enum_methods_module
@_enum_methods_module ||= begin
mod = Module.new
include mod
mod
end
end
ENUM_CONFLICT_MESSAGE = \
"You tried to define an enum named \"%{enum}\" on the model \"%{klass}\", but " \
"this will generate a %{type} method \"%{method}\", which is already defined " \
"by %{source}."
def detect_enum_conflict!(enum_name, method_name, klass_method = false)
if klass_method && dangerous_class_method?(method_name)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'class',
method: method_name,
source: 'Active Record'
}
elsif !klass_method && dangerous_attribute_method?(method_name)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'instance',
method: method_name,
source: 'Active Record'
}
elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'instance',
method: method_name,
source: 'another enum'
}
end
end
end
end
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