Hello Everyone,

As we know that in almost all web applications there are certain things which need validations to be performed on

them. Validations can be performed in two ways that is client side and server side.

Client side validations are performed at the front end normally through java script and HTML's built in validations.

Server side validations are validations which are performed at the back end which are more secured and provides 

utmost security when compared to client side validations.

So here are some useful server side validations provided to us by active records which we can use in our web apps

• Format

This validation validates the attributes by testing if they match the defined format of the regular expression which is

specified using the :with expression

class User < ActiveRecord::Base
  validates :name, format: { with: /\A[a-zA-Z]+\z/,
    message: "only allows letters" }
end

• Inclusion

This validation validates the attributes by testing if the attribute values are included in the given set or not. If the 

values wont match with the given set then we can display an error message like this

class Shirt < ActiveRecord::Base
  validates :size, inclusion: { in: %w(small medium large),
    message: "%{value} is not a valid size" }
end

• Length

This validation validates the length of the attributes in many ways in which we can add different constraints as 

follows

class Employee < ActiveRecord::Base
  validates :name, length: { minimum: 20 }
  validates :address, length: { maximum: 500 }
  validates :password, length: { in: 8..20 }
  validates :account_number, length: { is: 8 }
end

• Uniqueness

This validation validates the attributes by testing if the value is already present in the table or not. It wont let the

value to get saved into the table unless and until the value is unique and is already not present in the table.

class User < ActiveRecord::Base
  validates :email, uniqueness: true
end

So these were some useful server side validations which we can use in our web apps.