Added ActiveRecord::Base#enum for declaring enum attributes where the values map to integers in the database, but can be queried by name

3 files changed, 62 insertions, 0 deletions

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index f19f5ecdf9..7a2c5c8bf2 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -37,6 +37,7 @@ module ActiveRecord
   autoload :ConnectionHandling
   autoload :CounterCache
   autoload :DynamicMatchers
+  autoload :Enum
   autoload :Explain
   autoload :Inheritance
   autoload :Integration
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 04e3dd49e7..69a9eabefb 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -291,6 +291,7 @@ module ActiveRecord #:nodoc:
     extend Translation
     extend DynamicMatchers
     extend Explain
+    extend Enum
     extend Delegation::DelegateCache
 
     include Persistence
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
new file mode 100644
index 0000000000..13b843ff4f
--- /dev/null
+++ b/activerecord/lib/active_record/enum.rb
@@ -0,0 +1,60 @@
+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: %i( 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 :conversation do
+  #     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"
+
+        values.each_with_index 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