diff --git a/app/models/user.rb b/app/models/user.rb
index e029173..fdbe3e4 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -9,5 +9,27 @@ class User < ActiveRecord::Base
   validates :email, format: {with: /\A[a-zA-Z0-9\-]+@[a-zA-Z0-9-]+\.(org|com|cn|io|net|cc|me)\z/}, uniqueness: true
   validates :password, length: {minimum: 6}, confirmation: true, if: :need_valid_password?
   validates :nick_name, length: {minimum: 2, maximum: 20}, uniqueness: true, if: 'nick_name.present?'
+  def nickname
+      self.nick_name || self.username
+  end
 
+  def set_admin
+      self.admin = 0 unless self.admin.present?
+  end
+
+  def check_password(password)
+      self.authenticate(password)
+  end
+
+  def update_last_reply_time
+      self.update_attribute last_reply_time: DateTime.now
+  end
+
+  def can_reply?
+      (DateTime.now.to_i - self.last_reply_time.to_i) > 60
+  end
+
+  def need_valid_password?
+      new_record? || password.present?
+  end
 end