Add SubclassTracking module.

lib/sidetiq/subclass_tracking.rb

@@ -0,0 +1,20 @@
+module Sidetiq
+  module SubclassTracking
+    def subclasses(deep = false)
+      @subclasses ||= []
+
+      if deep
+        @subclasses.inject([]) do |all, subclass|
+          (all << subclass) + subclass.subclasses(true)
+        end
+      else
+        @subclasses
+      end
+    end
+
+    def inherited(klass)
+      super
+      subclasses << klass
+    end
+  end
+end

test/test_subclass_tracking.rb

@@ -0,0 +1,22 @@
+require_relative 'helper'
+
+class TestSubclassTracking < Sidetiq::TestCase
+  class Foo
+    extend Sidetiq::SubclassTracking
+  end
+
+  class Bar < Foo
+  end
+
+  class Baz < Bar
+  end
+
+  def test_subclasses_non_recursive
+    assert_equal [Bar], Foo.subclasses
+  end
+
+  def test_subclasses_recursive
+    assert_equal [Bar, Baz], Foo.subclasses(true)
+  end
+end
+