Optimised performance for attribute extraction

Disabled all instrumentation unless enabled explicitly

bench/perf.rb

@@ -0,0 +1,52 @@
+require "rubygems"
+require "bundler/setup"
+require "active_model_serializers"
+require "active_support/json"
+require "benchmark"
+
+class User < Struct.new(:id,:name,:age,:about) 
+  include ActiveModel::SerializerSupport
+  
+  def fast_hash
+    h = { 
+      id: read_attribute_for_serialization(:id), 
+      name: read_attribute_for_serialization(:name), 
+      about: read_attribute_for_serialization(:about)
+    }
+    h[:age] = read_attribute_for_serialization(:age) if age > 18
+    h
+  end
+end
+
+class UserSerializer < ActiveModel::Serializer
+  attributes :id, :name, :age, :about
+
+  def include_age?
+    object.age > 18
+  end
+end
+
+
+
+u = User.new(1, "sam", 10, "about")
+s = UserSerializer.new(u)
+
+u2 = User.new(2, "sam", 20, "about")
+s2 = UserSerializer.new(u2)
+
+p s2.attributes
+
+p s.attributes
+
+
+n = 100000
+
+Benchmark.bmbm {|x| 
+  x.report("init") { n.times { UserSerializer.new(u) } }
+  x.report("fast_hash") { n.times { u.fast_hash } }
+  x.report("attributes") { n.times { UserSerializer.new(u).attributes } } 
+  x.report("serializable_hash") { n.times { UserSerializer.new(u).serializable_hash } }
+  x.report("serializable_hash_with_instrumentation") { n.times { UserSerializer.new(u).serializable_hash_with_instrumentation } }
+}   
+
+