Module ActiveRecord::Validations
In: vendor/rails/activerecord/lib/active_record/validations.rb

Please do have a look at ActiveRecord::Validations::ClassMethods for a higher level of validations.

Active Records implement validation by overwriting Base#validate (or the variations, validate_on_create and validate_on_update). Each of these methods can inspect the state of the object, which usually means ensuring that a number of attributes have a certain value (such as not empty, within a given range, matching a certain regular expression).

Example:

  class Person < ActiveRecord::Base
    protected
      def validate
        errors.add_on_empty %w( first_name last_name )
        errors.add("phone_number", "has invalid format") unless phone_number =~ /[0-9]*/
      end

      def validate_on_create # is only run the first time a new object is saved
        unless valid_discount?(membership_discount)
          errors.add("membership_discount", "has expired")
        end
      end

      def validate_on_update
        errors.add_to_base("No changes have occurred") if unchanged_attributes?
      end
  end

  person = Person.new("first_name" => "David", "phone_number" => "what?")
  person.save                         # => false (and doesn't do the save)
  person.errors.empty?                # => false
  person.errors.count                 # => 2
  person.errors.on "last_name"        # => "can't be empty"
  person.errors.on "phone_number"     # => "has invalid format"
  person.errors.each_full { |msg| puts msg }
                                      # => "Last name can't be empty\n" +
                                      #    "Phone number has invalid format"

  person.attributes = { "last_name" => "Heinemeier", "phone_number" => "555-555" }
  person.save # => true (and person is now saved in the database)

An Errors object is automatically created for every Active Record.

Methods

Classes and Modules

Module ActiveRecord::Validations::ClassMethods

Constants

VALIDATIONS = %w( validate validate_on_create validate_on_update )

Public Instance methods

Returns the Errors object that holds all information about attribute error messages.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1118
1118:     def errors
1119:       @errors ||= Errors.new(self)
1120:     end

Performs the opposite of valid?. Returns true if errors were added, false otherwise.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1113
1113:     def invalid?
1114:       !valid?
1115:     end

The validation process on save can be skipped by passing false. The regular Base#save method is replaced with this when the validations module is mixed in, which it is by default.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1076
1076:     def save_with_validation(perform_validation = true)
1077:       if perform_validation && valid? || !perform_validation
1078:         save_without_validation
1079:       else
1080:         false
1081:       end
1082:     end

Attempts to save the record just like Base#save but will raise a RecordInvalid exception instead of returning false if the record is not valid.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1086
1086:     def save_with_validation!
1087:       if valid?
1088:         save_without_validation!
1089:       else
1090:         raise RecordInvalid.new(self)
1091:       end
1092:     end

Runs validate and validate_on_create or validate_on_update and returns true if no errors were added otherwise false.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1095
1095:     def valid?
1096:       errors.clear
1097: 
1098:       run_callbacks(:validate)
1099:       validate
1100: 
1101:       if new_record?
1102:         run_callbacks(:validate_on_create)
1103:         validate_on_create
1104:       else
1105:         run_callbacks(:validate_on_update)
1106:         validate_on_update
1107:       end
1108: 
1109:       errors.empty?
1110:     end

Protected Instance methods

Overwrite this method for validation checks on all saves and use Errors.add(field, msg) for invalid attributes.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1124
1124:       def validate
1125:       end

Overwrite this method for validation checks used only on creation.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1128
1128:       def validate_on_create
1129:       end

Overwrite this method for validation checks used only on updates.

[Source]

      # File vendor/rails/activerecord/lib/active_record/validations.rb, line 1132
1132:       def validate_on_update
1133:       end

[Validate]