Moving the $inc atomic modifier over with its brothers and sisters.

- Refactored inc to truly be atomic like the others (remove dirty
  changes) and changed it's internal structure to match the other
  operations.

lib/mongoid.rb

@@ -69,7 +69,6 @@
 require "mongoid/keys"
 require "mongoid/logger"
 require "mongoid/matchers"
-require "mongoid/modifiers"
 require "mongoid/multi_parameter_attributes"
 require "mongoid/multi_database"
 require "mongoid/named_scope"

lib/mongoid/components.rb

@@ -29,7 +29,6 @@ module Components #:nodoc
     include Mongoid::JSON
     include Mongoid::Keys
     include Mongoid::Matchers
-    include Mongoid::Modifiers
     include Mongoid::NamedScope
     include Mongoid::NestedAttributes
     include Mongoid::Paths

lib/mongoid/persistence/atomic.rb

@@ -1,6 +1,7 @@
 # encoding: utf-8
 require "mongoid/persistence/atomic/operation"
 require "mongoid/persistence/atomic/add_to_set"
+require "mongoid/persistence/atomic/inc"
 require "mongoid/persistence/atomic/pull_all"
 require "mongoid/persistence/atomic/push"
 
@@ -30,6 +31,24 @@ def add_to_set(field, value, options = {})
         AddToSet.new(self, field, value, options).persist
       end
 
+      # Performs an atomic $inc of the provided value on the supplied
+      # field. If the field does not exist it will be initialized as
+      # the provided value.
+      #
+      # @example Increment a field.
+      #   person.inc(:score, 2)
+      #
+      # @param [ Symbol ] field The name of the field.
+      # @param [ Integer ] value The value to increment.
+      # @param [ Hash ] options The mongo persistence options.
+      #
+      # @return [ Array<Object> ] The new value of the field.
+      #
+      # @since 2.0.0
+      def inc(field, value, options = {})
+        Inc.new(self, field, value, options).persist
+      end
+
       # Performs an atomic $pullAll of the provided value on the supplied
       # field. If the field does not exist it will be initialized as an
       # empty array.
@@ -38,7 +57,7 @@ def add_to_set(field, value, options = {})
       #   person.pull_all(:aliases, [ "Bond", "James" ])
       #
       # @param [ Symbol ] field The name of the field.
-      # @param [ Object ] value The value to push.
+      # @param [ Array<Object> ] value The values to pull.
       # @param [ Hash ] options The mongo persistence options.
       #
       # @return [ Array<Object> ] The new value of the field.

lib/mongoid/persistence/atomic/inc.rb

@@ -0,0 +1,42 @@
+# encoding: utf-8
+module Mongoid #:nodoc:
+  module Persistence #:nodoc:
+    module Atomic #:nodoc:
+
+      # This class provides atomic $inc behaviour.
+      class Inc < Operation
+
+        # Sends the atomic $inc operation to the database.
+        #
+        # @example Persist the new values.
+        #   inc.persist
+        #
+        # @return [ Object ] The new integer value.
+        #
+        # @since 2.0.0
+        def persist
+          current = document[field] || 0
+          document[field] = current + value
+          document[field].tap do
+            document.collection.update(document._selector, operation, options)
+            document.changes.delete(field.to_s)
+          end
+        end
+
+        private
+
+        # Get the atomic operation to perform.
+        #
+        # @example Get the operation.
+        #   inc.operation
+        #
+        # @return [ Hash ] The $push operation for the field and addition.
+        #
+        # @since 2.0.0
+        def operation
+          { "$inc" => { field => value } }
+        end
+      end
+    end
+  end
+end

spec/functional/mongoid/persistence/atomic/inc_spec.rb

@@ -0,0 +1,88 @@
+require "spec_helper"
+
+describe Mongoid::Persistence::Atomic::Inc do
+
+  before do
+    Person.delete_all
+  end
+
+  describe "#inc" do
+
+    let(:person) do
+      Person.create(:ssn => "777-66-1010", :age => 100)
+    end
+
+    let(:reloaded) do
+      person.reload
+    end
+
+    context "when incrementing a field with a value" do
+
+      let!(:inced) do
+        person.inc(:age, 2)
+      end
+
+      it "increments by the provided value" do
+        person.age.should == 102
+      end
+
+      it "returns the new value" do
+        inced.should == 102
+      end
+
+      it "persists the changes" do
+        reloaded.age.should == 102
+      end
+
+      it "resets the dirty attributes" do
+        person.changes["age"].should be_nil
+      end
+    end
+
+    context "when incrementing a nil field" do
+
+      let!(:inced) do
+        person.inc(:score, 2)
+      end
+
+      it "sets the value to the provided number" do
+        person.score.should == 2
+      end
+
+      it "returns the new value" do
+        inced.should == 2
+      end
+
+      it "persists the changes" do
+        reloaded.score.should == 2
+      end
+
+      it "resets the dirty attributes" do
+        person.changes["score"].should be_nil
+      end
+    end
+
+    context "when incrementing a non existant field" do
+
+      let!(:inced) do
+        person.inc(:high_score, 5)
+      end
+
+      it "sets the value to the provided number" do
+        person.high_score.should == 5
+      end
+
+      it "returns the new value" do
+        inced.should == 5
+      end
+
+      it "persists the changes" do
+        reloaded.high_score.should == 5
+      end
+
+      it "resets the dirty attributes" do
+        person.changes["high_score"].should be_nil
+      end
+    end
+  end
+end