Allows you to check if an attribute has changed to a particular value

model.name_changed?(from: "Pete", to: "Ringo")

3 files changed, 22 insertions, 2 deletions

diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 77d1252f1f..42cf58a870 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   `attribute_changed?` now accepts parameters which check the old and new value of the attribute
+
+    `model.name_changed?(from: "Pete", to: "Ringo")`
+
+    *Tejas Dinkar*
+
 *   Fix `has_secure_password` to honor bcrypt-ruby's cost attribute.
 
     *T.J. Schuck*
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 8ccb25c613..58d87e6f7f 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -54,6 +54,7 @@ module ActiveModel
   #   person.name = 'Bob'
   #   person.changed?       # => true
   #   person.name_changed?  # => true
+  #   person.name_changed?(from: "Uncle Bob", to: "Bob") # => true
   #   person.name_was       # => "Uncle Bob"
   #   person.name_change    # => ["Uncle Bob", "Bob"]
   #   person.name = 'Bill'
@@ -149,8 +150,11 @@ module ActiveModel
     end
 
     # Handle <tt>*_changed?</tt> for +method_missing+.
-    def attribute_changed?(attr) # :nodoc:
-      changed_attributes.include?(attr)
+    def attribute_changed?(attr, options = {}) #:nodoc:
+      result = changed_attributes.include?(attr)
+      result &&= options[:to] == __send__(attr) if options.key?(:to)
+      result &&= options[:from] == changed_attributes[attr] if options.key?(:from)
+      result
     end
 
     # Handle <tt>*_was</tt> for +method_missing+.
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index a90d0b1299..54427a1513 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -67,6 +67,16 @@ class DirtyTest < ActiveModel::TestCase
     assert_equal [nil, "John"], @model.changes['name']
   end
 
+  test "checking if an attribute has changed to a particular value" do
+    @model.name = "Ringo"
+    assert @model.name_changed?(from: nil, to: "Ringo")
+    assert_not @model.name_changed?(from: "Pete", to: "Ringo")
+    assert @model.name_changed?(to: "Ringo")
+    assert_not @model.name_changed?(to: "Pete")
+    assert @model.name_changed?(from: nil)
+    assert_not @model.name_changed?(from: "Pete")
+  end
+
   test "changes accessible through both strings and symbols" do
     @model.name = "David"
     assert_not_nil @model.changes[:name]