From b9a1e9a4b2289de199b214a542aa9fd3cb19be54 Mon Sep 17 00:00:00 2001
From: Michael Ryan <perceptec@gmail.com>
Date: Wed, 18 Feb 2015 17:55:48 -0500
Subject: Add `ActiveRecord::Base.suppress`

---
 activerecord/lib/active_record/suppressor.rb | 55 ++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 activerecord/lib/active_record/suppressor.rb

(limited to 'activerecord/lib/active_record/suppressor.rb')

diff --git a/activerecord/lib/active_record/suppressor.rb b/activerecord/lib/active_record/suppressor.rb
new file mode 100644
index 0000000000..b47f02143c
--- /dev/null
+++ b/activerecord/lib/active_record/suppressor.rb
@@ -0,0 +1,55 @@
+module ActiveRecord
+  # ActiveRecord::Suppressor prevents the receiver from being saved during
+  # a given block.
+  #
+  # For example, here's a pattern of creating notifications when new comments
+  # are posted. (The notification may in turn trigger an email, a push
+  # notification, or just appear in the UI somewhere):
+  # 
+  # class Comment < ActiveRecord::Base
+  #   belongs_to :commentable, polymorphic: true
+  #   after_create -> { Notification.create! comment: self,
+  #     recipients: commentable.recipients }
+  # end
+  # 
+  # That's what you want the bulk of the time. New comment creates a new
+  # Notification. But there may well be off cases, like copying a commentable
+  # and its comments, where you don't want that. So you'd have a concern
+  # something like this:
+  # 
+  # module Copyable
+  #   def copy_to(destination)
+  #     Notification.suppress do
+  #       # Copy logic that creates new comments that we do not want
+  #       # triggering notifications.
+  #     end
+  #   end
+  # end
+  module Suppressor
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      def suppress(&block)
+        SuppressorRegistry.suppressed[name] = true
+        yield
+      ensure
+        SuppressorRegistry.suppressed[name] = false
+      end
+    end
+
+    # Ignore saving events if we're in suppression mode.
+    def save!(*args)
+      SuppressorRegistry.suppressed[self.class.name] ? self : super
+    end
+  end
+
+  class SuppressorRegistry # :nodoc:
+    extend ActiveSupport::PerThreadRegistry
+
+    attr_reader :suppressed
+
+    def initialize
+      @suppressed = {}
+    end
+  end
+end
-- 
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