diff --git a/application_record.rb b/application_record.rb
new file mode 100644
index 0000000..10a4cba
--- /dev/null
+++ b/application_record.rb
@@ -0,0 +1,3 @@
+class ApplicationRecord < ActiveRecord::Base
+  self.abstract_class = true
+end
diff --git a/concerns/.keep b/concerns/.keep
new file mode 100644
index 0000000..e69de29
diff --git a/user.rb b/user.rb
new file mode 100644
index 0000000..140793e
--- /dev/null
+++ b/user.rb
@@ -0,0 +1,23 @@
+class User < ApplicationRecord
+  validates :name, presence: true
+  validates :phone, numericality: true
+  validates :ngaysinh, presence: true
+  validate :check_length, :check_ngaysinh, :check_phone
+  private
+  def check_length
+    if self.name && self.name.length < 30
+      self.errors.add :name, "ten qua ngan"
+    end
+  end
+  def check_ngaysinh
+    t = Time.now
+    if self.ngaysinh && (self.ngaysinh.year < t.year - 90 || self.ngaysinh.year > t.year - 7)
+      self.errors.add :ngaysinh, "khong hop tuoi"
+    end
+  end
+  def check_phone
+    unless self.phone.length == 10 && self.phone[0] == 0
+      self.errors.add :phone, "khong hop le"
+    end
+  end
+end