Dependor singleton

README.md

@@ -249,7 +249,7 @@ require 'dependor/shorty'
 
 class MyInjector
   include Dependor::AutoInject
-  
+
   takes :params, :session, :request
 
   def foo
@@ -274,6 +274,38 @@ class PostsController < ApplicationController
 end
 ```
 
+## Dependor::Singleton
+
+You can include this to make your service class as a singleton.
+
+```ruby
+class FooService
+  include Dependor::Singleton
+end
+
+class MyInjector
+  include Dependor::AutoInject
+
+  takes :params, :session, :request
+end
+
+class ApplicationController
+  extend Dependor::Injectable
+
+  def injector
+    @injector ||= MyInjector.new(params, session, request)
+  end
+end
+
+class PostsController < ApplicationController
+  inject :foo_service
+
+  def get
+    render text: foo_service.object_id == foo_service.object_id # true
+  end
+end
+```
+
 ## Testing
 
 Dependor doesn't add any dependencies to your classes so you can test them any way you like.

lib/dependor.rb

@@ -10,6 +10,7 @@ module Dependor
   autoload :Injectable,           'dependor/injectable'
   autoload :Instantiator,         'dependor/instantiator'
   autoload :Isolate,              'dependor/isolate'
+  autoload :Singleton,            'dependor/singleton'
   autoload :Let,                  'dependor/let'
   autoload :SendingInjector,      'dependor/sending_injector'
   autoload :Shorty,               'dependor/shorty'

lib/dependor/instantiator.rb

@@ -5,11 +5,16 @@ class Instantiator
     def initialize(injector, dependency_names)
       @injector = injector
       @dependency_names = dependency_names
+      @singletons = {}
     end
 
     def instantiate(klass)
       dependencies = dependency_names.for_class(klass).map{|name| @injector.get(name)}
-      return klass.new(*dependencies)
+      if klass.include?(Dependor::Singleton)
+        return @singletons[klass] ||= klass.new(*dependencies)
+      else
+        return klass.new(*dependencies)
+      end
     end
   end
 end

lib/dependor/singleton.rb

@@ -0,0 +1,4 @@
+module Dependor
+  module Singleton
+  end
+end

spec/dependor/instantiator_spec.rb

@@ -35,4 +35,24 @@ def foo
 
     instance.foo.should == 'foo-bar-baz'
   end
+
+  it "instantiates objects as a new object" do
+    klass = Class.new {}
+
+    first_instance = instantiator.instantiate(klass)
+    second_instance = instantiator.instantiate(klass)
+
+    first_instance.object_id.should_not == second_instance.object_id
+  end
+
+  it "instantiates objects as a singleton object" do
+    klass = Class.new do
+      include Dependor::Singleton
+    end
+
+    first_instance = instantiator.instantiate(klass)
+    second_instance = instantiator.instantiate(klass)
+
+    first_instance.object_id.should == second_instance.object_id
+  end
 end