3 files changed, 6 insertions, 14 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