Class: ActiveModel::Validator

Inherits:
Object
  • Object
show all
Defined in:
activemodel/lib/active_model/validator.rb

Overview

Active Model Validator

A simple base class that can be used along with ActiveModel::Validations::ClassMethods.validates_with

class Person
  include ActiveModel::Validations
  validates_with MyValidator
end

class MyValidator < ActiveModel::Validator
  def validate(record)
    if some_complex_logic
      record.errors[:base] = "This record is invalid"
    end
  end

  private
    def some_complex_logic
      # ...
    end
end

Any class that inherits from ActiveModel::Validator must implement a method called validate which accepts a record.

class Person
  include ActiveModel::Validations
  validates_with MyValidator
end

class MyValidator < ActiveModel::Validator
  def validate(record)
    record # => The person instance being validated
    options # => Any non-standard options passed to validates_with
  end
end

To cause a validation error, you must add to the record‘s errors directly from within the validators message

class MyValidator < ActiveModel::Validator
  def validate(record)
    record.errors[:base] << "This is some custom error message"
    record.errors[:first_name] << "This is some complex validation"
    # etc...
  end
end

To add behavior to the initialize method, use the following signature:

class MyValidator < ActiveModel::Validator
  def initialize(record, options)
    super
    @my_custom_field = options[:field_name] || :first_name
  end
end

The easiest way to add custom validators for validating individual attributes is with the convenient ActiveModel::EachValidator. For example:

class TitleValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors[attribute] << 'must be Mr. Mrs. or Dr.' unless value.in?(['Mr.', 'Mrs.', 'Dr.'])
  end
end

This can now be used in combination with the validates method (see ActiveModel::Validations::ClassMethods.validates for more on this)

class Person
  include ActiveModel::Validations
  attr_accessor :title

  validates :title, :presence => true
end

Validator may also define a setup instance method which will get called with the class that using that validator as its argument. This can be useful when there are prerequisites such as an attr_accessor being present for example:

class MyValidator < ActiveModel::Validator
  def setup(klass)
    klass.send :attr_accessor, :custom_attribute
  end
end

This setup method is only called when used with validation macros or the class level validates_with method.

Direct Known Subclasses

EachValidator

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options) ⇒ Validator

Accepts options that will be made available through the options reader.



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# File 'activemodel/lib/active_model/validator.rb', line 112

def initialize(options)
  @options = options.freeze
end

Instance Attribute Details

#options ⇒ Object (readonly)

Returns the value of attribute options



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# File 'activemodel/lib/active_model/validator.rb', line 100

def options
  @options
end

Class Method Details

.kind ⇒ Object

Returns the kind of the validator. Examples:

PresenceValidator.kind   # => :presence
UniquenessValidator.kind # => :uniqueness



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# File 'activemodel/lib/active_model/validator.rb', line 107

def self.kind
  @kind ||= name.split('::').last.underscore.sub(/_validator$/, '').to_sym unless anonymous?
end

Instance Method Details

#kind ⇒ Object

Return the kind for this validator.



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# File 'activemodel/lib/active_model/validator.rb', line 117

def kind
  self.class.kind
end

#validate(record) ⇒ Object

Override this method in subclasses with validation logic, adding errors to the records errors array where necessary.

Raises:

  • (NotImplementedError) 


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# File 'activemodel/lib/active_model/validator.rb', line 123

def validate(record)
  raise NotImplementedError, "Subclasses must implement a validate(record) method."
end