Refactor PerformableMethod so it's easier to extend with multiple bac…

…kends

lib/delayed/backend/active_record.rb

@@ -1,5 +1,15 @@
 require 'timeout'
 
+class ActiveRecord::Base
+  def self.load_for_delayed_job(id)
+    find(id)
+  end
+
+  def dump_for_delayed_job
+    "#{self.class};#{id}"
+  end
+end
+
 module Delayed
   module Backend
     module ActiveRecord

lib/delayed/backend/mongo.rb

@@ -1,5 +1,21 @@
 require 'mongo_mapper'
 
+module MongoMapper
+  module Document
+    module ClassMethods
+      def load_for_delayed_job(id)
+        find!(id)
+      end
+    end
+
+    module InstanceMethods
+      def dump_for_delayed_job
+        "#{self.class};#{id}"
+      end
+    end
+  end
+end
+
 module Delayed
   module Backend
     module Mongo

lib/delayed/performable_method.rb

@@ -1,8 +1,16 @@
+class Class
+  def load_for_delayed_job(arg)
+    self
+  end
+
+  def dump_for_delayed_job
+    name
+  end
+end
+
 module Delayed
   class PerformableMethod < Struct.new(:object, :method, :args)
-    CLASS_STRING_FORMAT = /^CLASS\:([A-Z][\w\:]+)$/
-    AR_STRING_FORMAT    = /^AR\:([A-Z][\w\:]+)\:(\d+)$/
-    MM_STRING_FORMAT    = /^MM\:([A-Z][\w\:]+)\:(\w+)$/
+    STRING_FORMAT = /^LOAD\;([A-Z][\w\:]+)(?:\;(\w+))?$/
 
     class LoadError < StandardError
     end
@@ -15,42 +23,39 @@ def initialize(object, method, args)
       self.method = method.to_sym
     end
 
-    def display_name  
-      case self.object
-      when CLASS_STRING_FORMAT then "#{$1}.#{method}"
-      when AR_STRING_FORMAT    then "#{$1}##{method}"
-      when MM_STRING_FORMAT    then "#{$1}##{method}"
-      else "Unknown##{method}"
-      end      
-    end    
-
+    def display_name
+      if STRING_FORMAT === object
+        "#{$1}#{$2 ? '#' : '.'}#{method}"
+      else
+        "#{object.class}##{method}"
+      end
+    end
+
     def perform
       load(object).send(method, *args.map{|a| load(a)})
     rescue PerformableMethod::LoadError
-      # We cannot do anything about objects which were deleted in the meantime
+      # We cannot do anything about objects that can't be loaded
       true
     end
 
     private
 
     def load(obj)
-      case obj
-      when CLASS_STRING_FORMAT then $1.constantize
-      when AR_STRING_FORMAT    then $1.constantize.find($2)
-      when MM_STRING_FORMAT    then $1.constantize.find!($2)
-      else obj
+      if STRING_FORMAT === obj
+        $1.constantize.load_for_delayed_job($2)
+      else
+        obj
       end
     rescue => e
       Delayed::Worker.logger.warn "Could not load object for job: #{e.message}"
       raise PerformableMethod::LoadError
     end
 
     def dump(obj)
-      case obj
-      when Class                  then "CLASS:#{obj.name}"
-      when ActiveRecord::Base     then "AR:#{obj.class}:#{obj.id}"
-      when MongoMapper::Document  then "MM:#{obj.class}:#{obj.id}"
-      else obj
+      if obj.respond_to?(:dump_for_delayed_job)
+        "LOAD;#{obj.dump_for_delayed_job}"
+      else
+        obj
       end
     end
   end

spec/delayed_method_spec.rb

@@ -11,15 +11,6 @@ def say_hello
   end
 end
 
-class ErrorObject
-
-  def throw
-    raise ActiveRecord::RecordNotFound, '...'
-    false
-  end
-
-end
-
 class StoryReader
 
   def read(story)
@@ -65,7 +56,9 @@ def read(story)
   end
 
   it "should ignore ActiveRecord::RecordNotFound errors because they are permanent" do
-    job = ErrorObject.new.send_later(:throw)
+    story = Story.create :text => 'Once upon...'
+    job = story.send_later(:tell)
+    story.destroy
     lambda { job.invoke_job }.should_not raise_error
   end
 
@@ -75,7 +68,7 @@ def read(story)
 
     job =  Delayed::Job.find(:first)
     job.payload_object.class.should   == Delayed::PerformableMethod
-    job.payload_object.object.should  == "AR:Story:#{story.id}"
+    job.payload_object.object.should  == "LOAD;Story;#{story.id}"
     job.payload_object.method.should  == :tell
     job.payload_object.args.should    == []
     job.payload_object.perform.should == 'Once upon...'
@@ -91,7 +84,7 @@ def read(story)
     job =  Delayed::Job.find(:first)
     job.payload_object.class.should   == Delayed::PerformableMethod
     job.payload_object.method.should  == :read
-    job.payload_object.args.should    == ["AR:Story:#{story.id}"]
+    job.payload_object.args.should    == ["LOAD;Story;#{story.id}"]
     job.payload_object.perform.should == 'Epilog: Once upon...'
   end                 
 

spec/mongo_job_spec.rb

@@ -44,7 +44,7 @@ def tell
       job = story.send_later(:tell)
 
       job.payload_object.class.should   == Delayed::PerformableMethod
-      job.payload_object.object.should  == "MM:MongoStory:#{story.id}"
+      job.payload_object.object.should  == "LOAD;MongoStory;#{story.id}"
       job.payload_object.method.should  == :tell
       job.payload_object.args.should    == []
       job.payload_object.perform.should == 'Once upon a time…'
@@ -55,7 +55,7 @@ def tell
       job = MongoStoryReader.new.send_later(:read, story)
       job.payload_object.class.should   == Delayed::PerformableMethod
       job.payload_object.method.should  == :read
-      job.payload_object.args.should    == ["MM:MongoStory:#{story.id}"]
+      job.payload_object.args.should    == ["LOAD;MongoStory;#{story.id}"]
       job.payload_object.perform.should == 'Epilog: Once upon a time…'
     end
   end