diff --git a/app/models/metadata_path.rb b/app/models/metadata_path.rb
index 7f386928..5dc25c8b 100644
--- a/app/models/metadata_path.rb
+++ b/app/models/metadata_path.rb
@@ -8,7 +8,8 @@ class MetadataPath < MetadataTemplate
   end
 
   def value
-    default_value
+    @value_was ||= default_value
+    self[:value] = default_value
   end
   alias absolute value
   alias to_s value
diff --git a/app/models/metadata_template.rb b/app/models/metadata_template.rb
index 35dbf455..521a02a8 100644
--- a/app/models/metadata_template.rb
+++ b/app/models/metadata_template.rb
@@ -10,6 +10,17 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
                               :layout, keyword_init: true) do
   include ActionText::ContentHelper
 
+  attr_reader :value_was
+
+  def value=(new_value)
+    @value_was = value
+    self[:value] = new_value
+  end
+
+  def changed?
+    !value_was.nil? && value_was != value
+  end
+
   # El valor por defecto
   def default_value
     raise NotImplementedError
diff --git a/app/models/post.rb b/app/models/post.rb
index 215a8ef0..4a80cab5 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -11,6 +11,7 @@ class Post < OpenStruct
   # Otros atributos que no vienen en los metadatos
   PRIVATE_ATTRIBUTES = %i[path slug attributes errors].freeze
   PUBLIC_ATTRIBUTES = %i[lang date uuid].freeze
+  ATTR_SUFFIXES = %w[? =].freeze
 
   class << self
     # Obtiene el layout sin leer el Document
@@ -117,10 +118,6 @@ class Post < OpenStruct
                                   method: mid)
     end
 
-    # Definir los attribute_*
-    new_attribute_was(name)
-    new_attribute_changed(name)
-
     # OpenStruct
     super(mid, *args)
 
@@ -193,7 +190,7 @@ class Post < OpenStruct
   def save(validate: true)
     return false if validate && !valid?
     # Salir si tenemos que cambiar el nombre del archivo y no pudimos
-    return false if !new? && path_changed? && !update_path!
+    return false if !new? && path.changed? && !update_path!
     return false unless save_attributes!
     return false unless write
 
@@ -225,7 +222,7 @@ class Post < OpenStruct
   # existe el destino
   def update_path!
     !File.exist?(path.absolute) &&
-      FileUtils.mv(path_was, path.absolute) &&
+      FileUtils.mv(path.value_was, path.absolute) &&
       document.path = path.absolute
   end
 
@@ -299,38 +296,11 @@ class Post < OpenStruct
     document.data.fetch('usuaries', [])
   end
 
-  def new_attribute_was(method)
-    attr_was = "#{method}_was".to_sym
-    return attr_was if singleton_class.method_defined? attr_was
-
-    define_singleton_method(attr_was) do
-      name = attribute_name(attr_was)
-      if document.respond_to?(name)
-        document.send(name)
-      else
-        document.data[name.to_s]
-      end
-    end
-  end
-
-  # Pregunta si el atributo cambió
-  def new_attribute_changed(method)
-    attr_changed = "#{method}_changed?".to_sym
-
-    return attr_changed if singleton_class.method_defined? attr_changed
-
-    define_singleton_method(attr_changed) do
-      name = attribute_name(attr_changed)
-      name_was = (name.to_s + '_was').to_sym
-
-      (send(name).try(:value) || send(name)) != send(name_was)
-    end
-  end
-
   # Obtiene el nombre del atributo a partir del nombre del método
   def attribute_name(attr)
     # XXX: Los simbolos van al final
-    %w[_was _changed? ? =].reduce(attr.to_s) do |a, suffix|
+    @attribute_name_cache ||= {}
+    @attribute_name_cache[attr] ||= ATTR_SUFFIXES.reduce(attr.to_s) do |a, suffix|
       a.chomp suffix
     end.to_sym
   end
diff --git a/test/models/post_test.rb b/test/models/post_test.rb
index 0235970f..67dd1a24 100644
--- a/test/models/post_test.rb
+++ b/test/models/post_test.rb
@@ -98,36 +98,32 @@ class PostTest < ActiveSupport::TestCase
   test 'attribute_name' do
     assert_equal :hola, @post.send(:attribute_name, :hola)
     assert_equal :hola, @post.send(:attribute_name, :hola?)
-    assert_equal :hola, @post.send(:attribute_name, :hola_was)
-    assert_equal :hola, @post.send(:attribute_name, :hola_changed?)
   end
 
   test 'se puede cambiar el slug' do
     @post.title.value = SecureRandom.hex
-    assert_equal @post.slug_was, @post.slug.value
-    assert_not @post.slug_changed?
+    assert_not @post.slug.changed?
     assert @post.slug.valid?
 
     ex_slug = @post.slug.value
     @post.slug.value = SecureRandom.hex
 
     assert_not_equal ex_slug, @post.slug.value
-    assert_equal ex_slug, @post.slug_was
-    assert @post.slug_changed?
+    assert_equal ex_slug, @post.slug.value_was
+    assert @post.slug.changed?
     assert @post.slug.valid?
   end
 
   test 'se puede cambiar la fecha' do
-    assert_equal @post.date_was, @post.date.value
-    assert_not @post.date_changed?
+    assert_not @post.date.changed?
     assert @post.date.valid?
 
     ex_date = @post.date.value
     @post.date.value = 2.days.ago
 
     assert_not_equal ex_date, @post.date.value
-    assert_equal ex_date, @post.date_was
-    assert @post.date_changed?
+    assert_equal ex_date, @post.date.value_was
+    assert @post.date.changed?
     assert @post.date.valid?
   end
 
@@ -137,7 +133,7 @@ class PostTest < ActiveSupport::TestCase
     @post.slug.value = title = SecureRandom.hex
     @post.date.value = hoy
 
-    assert @post.path_changed?
+    assert @post.path.changed?
     assert_equal "_es/#{hoy.strftime('%F')}-#{title}.markdown",
                  @post.path.relative
 
@@ -165,7 +161,7 @@ class PostTest < ActiveSupport::TestCase
 
     assert_not @post.save
     assert File.exist?(@post.path.absolute)
-    assert File.exist?(@post.path_was)
+    assert File.exist?(@post.path.value_was)
   end
 
   test 'se pueden crear nuevos' do