Ruby on Rails - User Input Validations

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Here is the list of validations which you can perform on user input −

validates_presence_of

The following checks that last_name and first_name should be filled and should not be NULL.

validates_presence_of :firstname, :lastname

validates_length_of

The following example shows various validations on a single field. These validations can be performed separately.

validates_length_of :password,
   :minimum => 8           # more than 8 characters
   :maximum => 16          # shorter than 16 characters
   :in => 8..16            # between 8 and 16 characters
   :too_short => 'way too short'    
   :too_long => 'way to long'

validates_acceptance_of

The following will accept only 'Y' value for option field.

validates_acceptance_of :option            
                        :accept => 'Y' 

validates_confirmation_of

The fields password and password_confirmation must match and will be used as follows −

validates_confirmation_of :password

validates_uniqueness_of

The following puts a condition for user_name to be unique.

validates_uniqueness_of :user_name

validates_format_of

The following validates that a given email ID is in a valid format. This shows how you can use regular expression to validate a field.

validates_format_of :email
   :with => /^(+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i

validates_numericality_of

This validates that given field is numeric.

validates_numericality_of   :value                 
                            :only_integer => true   
                            :allow_nil => true      

validates_inclusion_of

The following checks that the passed value is an enumeration and falls in the given range.

validates_inclusion_of  :gender,   
                        :in => %w( m, f )

validates_exclusion_of

The following checks that the given values does not fall in the given range.

validates_exclusion_of  :age        
                        :in => 13..19

validates_inclusion_of

The following checks that the given values should fall in the given range. This is the opposite to validates_exclusion_of.

validates_inclusion_of  :age
                        :in => 13..19

validates_associated

This validates that the associated object is valid.

Options for all Validations

You can use the following options along with all the validations.

• :message => 'my own errormessage' Use this to print a custom error message in case of validation fails.

• :on => :create or :update This will be used in such cases where you want to perform validation only when record is being created or updated. So, if you use :create then this validation work only when there is a create operation on database.

Check the Validations link for more detail on Validations.