4 files changed, 6 insertions, 16 deletions
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 1361d327b3..1dfd0b6132 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -115,7 +115,7 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changes # => { 'name' => ['bill', 'bob'] }
     def changes
-      changed.inject(HashWithIndifferentAccess.new){ |h, attr| h[attr] = attribute_change(attr); h }
+      HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
     end
 
     # Map of attributes that were changed when the model was saved.
diff --git a/activemodel/lib/active_model/serialization.rb b/activemodel/lib/active_model/serialization.rb
index 8f90ef64ba..37739b98a1 100644
--- a/activemodel/lib/active_model/serialization.rb
+++ b/activemodel/lib/active_model/serialization.rb
@@ -79,15 +79,8 @@ module ActiveModel
         attribute_names -= except
       end
 
-      method_names = Array.wrap(options[:methods]).inject([]) do |methods, name|
-        methods << name if respond_to?(name.to_s)
-        methods
-      end
-
-      (attribute_names + method_names).inject({}) { |hash, name|
-        hash[name] = send(name)
-        hash
-      }
+      method_names = Array.wrap(options[:methods]).map { |n| n if respond_to?(n.to_s) }.compact
+      Hash[(attribute_names + method_names).map { |n| [n, send(n)] }]
     end
   end
 end
diff --git a/activemodel/lib/active_model/serializers/xml.rb b/activemodel/lib/active_model/serializers/xml.rb
index e89385e7e5..26a134568c 100644
--- a/activemodel/lib/active_model/serializers/xml.rb
+++ b/activemodel/lib/active_model/serializers/xml.rb
@@ -76,10 +76,9 @@ module ActiveModel
         end
 
         def serializable_methods
-          Array.wrap(options[:methods]).inject([]) do |methods, name|
-            methods << self.class::MethodAttribute.new(name.to_s, @serializable) if @serializable.respond_to?(name.to_s)
-            methods
-          end
+          Array.wrap(options[:methods]).map do |name|
+            self.class::MethodAttribute.new(name.to_s, @serializable) if @serializable.respond_to?(name.to_s)
+          end.compact
         end
 
         def serialize
diff --git a/activemodel/lib/active_model/validations/acceptance.rb b/activemodel/lib/active_model/validations/acceptance.rb
index d9dfe0c855..a7296d8e1d 100644
--- a/activemodel/lib/active_model/validations/acceptance.rb
+++ b/activemodel/lib/active_model/validations/acceptance.rb
@@ -14,8 +14,6 @@ module ActiveModel
       end
 
       def setup(klass)
-        # Note: instance_methods.map(&:to_s) is important for 1.9 compatibility
-        # as instance_methods returns symbols unlike 1.8 which returns strings.
         attr_readers = attributes.reject { |name| klass.attribute_method?(name) }
         attr_writers = attributes.reject { |name| klass.attribute_method?("#{name}=") }
         klass.send(:attr_reader, *attr_readers)