validate

application_record.rb

@@ -0,0 +1,3 @@
+class ApplicationRecord < ActiveRecord::Base
+  self.abstract_class = true
+end

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