1 files changed, 37 insertions, 0 deletions
diff --git a/app/validators/uniqueness_of_in_memory_validator.rb b/app/validators/uniqueness_of_in_memory_validator.rb
new file mode 100644
index 00000000000..84e88b2eb76
--- /dev/null
+++ b/app/validators/uniqueness_of_in_memory_validator.rb
@@ -0,0 +1,37 @@
+# UniquenessOfInMemoryValidator
+#
+# This validtor is designed for especially the following condition
+# - Use `accepts_nested_attributes_for :xxx` in a parent model
+# - Use `validates :xxx, uniqueness: { scope: :xxx_id }` in a child model
+#
+# Inspired by https://stackoverflow.com/a/2883129/2522666
+module ActiveRecord
+  class Base
+    # Validate that the the objects in +collection+ are unique
+    # when compared against all their non-blank +attrs+. If not
+    # add +message+ to the base errors.
+    def validate_uniqueness_of_in_memory(collection, attrs, message)
+      hashes = collection.inject({}) do |hash, record|
+        key = attrs.map { |a| record.send(a).to_s }.join
+        if key.blank? || record.marked_for_destruction?
+          key = record.object_id
+        end
+        hash[key] = record unless hash[key]
+        hash
+      end
+
+      if collection.length > hashes.length
+        self.errors.add(*message)
+      end
+    end
+  end
+end
+
+class UniquenessOfInMemoryValidator < ActiveModel::Validator
+  def validate(record)
+    record.validate_uniqueness_of_in_memory(
+      record.public_send(options[:collection]),
+      options[:attrs],
+      options[:message])
+  end
+end