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.add(: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.add :base, "This is some custom error message"
record.errors.add :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(options)
super
@my_custom_field = options[:field_name] || :first_name
end
end
Note that the validator is initialized only once for the whole application life cycle, and not on each validation run.
The easiest way to add custom validators for validating individual attributes is with the convenient ActiveModel::EachValidator
.
class TitleValidator < ActiveModel::EachValidator
def validate_each(record, attribute, value)
record.errors.add attribute, 'must be Mr., Mrs., or Dr.' unless %w(Mr. Mrs. Dr.).include?(value)
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, title: true
end
It can be useful to access the class that is using that validator when there are prerequisites such as an attr_accessor
being present. This class is accessible via options[:class]
in the constructor. To set up your validator override the constructor.
class MyValidator < ActiveModel::Validator
def initialize(options={})
super
options[:class].attr_accessor :custom_attribute
end
end
Attributes
[R] | options |
Class Public methods
kind() Link
Returns the kind of the validator.
PresenceValidator.kind # => :presence
AcceptanceValidator.kind # => :acceptance
new(options = {}) Link
Accepts options that will be made available through the options
reader.
Instance Public methods
kind() Link
Returns the kind for this validator.
PresenceValidator.new(attributes: [:username]).kind # => :presence
AcceptanceValidator.new(attributes: [:terms]).kind # => :acceptance
validate(record) Link
Override this method in subclasses with validation logic, adding errors to the records errors
array where necessary.