Returns true if attribute is an attribute method, false otherwise.

class Person include ActiveModel::Validations attr_accessor :name end User.attribute_method?(:name) # => true User.attribute_method?(:age) # => false 

# File activemodel/lib/active_model/validations.rb, line 282 def attribute_method?(attribute) method_defined?(attribute) end

Clears all of the validators and validations.

Note that this will clear anything that is being used to validate the model for both the validates_with and validate methods. It clears the validators that are created with an invocation of validates_with and the callbacks that are set by an invocation of validate.

class Person include ActiveModel::Validations validates_with MyValidator validates_with OtherValidator, on: :create validates_with StrictValidator, strict: true validate :cannot_be_robot def cannot_be_robot errors.add(:base, 'A person cannot be a robot') if person_is_robot end end Person.validators # => [ # #<MyValidator:0x007fbff403e808 @options={}>, # #<OtherValidator:0x007fbff403d930 @options={on: :create}>, # #<StrictValidator:0x007fbff3204a30 @options={strict:true}> # ] 

If one runs Person.clear_validators! and then checks to see what validators this class has, you would obtain:

Person.validators # => [] 

Also, the callback set by validate :cannot_be_robot will be erased so that:

Person._validate_callbacks.empty? # => true 

# File activemodel/lib/active_model/validations.rb, line 246 def clear_validators! reset_callbacks(:validate) _validators.clear end

Adds a validation method or block to the class. This is useful when overriding the validate instance method becomes too unwieldy and you’re looking for more descriptive declaration of your validations.

This can be done with a symbol pointing to a method:

class Comment include ActiveModel::Validations validate :must_be_friends def must_be_friends errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee) end end 

With a block which is passed with the current record to be validated:

class Comment include ActiveModel::Validations validate do |comment| comment.must_be_friends end def must_be_friends errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee) end end 

Or with a block where self points to the current record to be validated:

class Comment include ActiveModel::Validations validate do errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee) end end 

Note that the return value of validation methods is not relevant. It’s not possible to halt the validate callback chain.

Options:

• :on - Specifies the contexts where this validation is active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. on: :create or on: :custom_validation_context or on: [:create, :custom_validation_context])

• :except_on - Specifies the contexts where this validation is not active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. except: :create or except_on: :custom_validation_context or except_on: [:create, :custom_validation_context])

• :if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.

• :unless - Specifies a method, proc, or string to call to determine if the validation should not occur (e.g. unless: :skip_validation, or unless: Proc.new { |user| user.signup_step <= 2 }). The method, proc, or string should return or evaluate to a true or false value.

NOTE: Calling validate multiple times on the same method will overwrite previous definitions.

# File activemodel/lib/active_model/validations.rb, line 160 def validate(*args, &block) options = args.extract_options! if args.all?(Symbol) options.each_key do |k| unless VALID_OPTIONS_FOR_VALIDATE.include?(k) raise ArgumentError.new("Unknown key: #{k.inspect}. Valid keys are: #{VALID_OPTIONS_FOR_VALIDATE.map(&:inspect).join(', ')}. Perhaps you meant to call `validates` instead of `validate`?") end end end if options.key?(:on) options = options.merge(if: [predicate_for_validation_context(options[:on]), *options[:if]]) end if options.key?(:except_on) options = options.dup options[:except_on] = Array(options[:except_on]) options[:unless] = [ ->(o) { options[:except_on].intersect?(Array(o.validation_context)) }, *options[:unless] ] end set_callback(:validate, *args, options, &block) end

This method is a shortcut to all default validators and any custom validator classes ending in ‘Validator’. Note that Rails default validators can be overridden inside specific classes by creating custom validator classes in their place such as PresenceValidator.

Examples of using the default Rails validators:

validates :username, absence: true validates :terms, acceptance: true validates :password, confirmation: true validates :username, exclusion: { in: %w(admin superuser) } validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i, on: :create } validates :age, inclusion: { in: 0..9 } validates :first_name, length: { maximum: 30 } validates :age, numericality: true validates :username, presence: true 

The power of the validates method comes when using custom validators and default validators in one call for a given attribute.

class EmailValidator < ActiveModel::EachValidator def validate_each(record, attribute, value) record.errors.add attribute, (options[:message] || "is not an email") unless /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i.match?(value) end end class Person include ActiveModel::Validations attr_accessor :name, :email validates :name, presence: true, length: { maximum: 100 } validates :email, presence: true, email: true end 

Validator classes may also exist within the class being validated allowing custom modules of validators to be included as needed.

class Film include ActiveModel::Validations class TitleValidator < ActiveModel::EachValidator def validate_each(record, attribute, value) record.errors.add attribute, "must start with 'the'" unless /\Athe/i.match?(value) end end validates :name, title: true end 

Additionally validator classes may be in another namespace and still used within any class.

validates :name, :'film/title' => true 

The validators hash can also handle regular expressions, ranges, arrays and strings in shortcut form.

validates :email, format: /@/ validates :role, inclusion: %w(admin contributor) validates :password, length: 6..20 

When using shortcut form, ranges and arrays are passed to your validator’s initializer as options[:in] while other types including regular expressions and strings are passed as options[:with].

There is also a list of options that could be used along with validators:

• :on - Specifies the contexts where this validation is active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. on: :create or on: :custom_validation_context or on: [:create, :custom_validation_context])

• :except_on - Specifies the contexts where this validation is not active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. except: :create or except_on: :custom_validation_context or except_on: [:create, :custom_validation_context])

• :if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.

• :unless - Specifies a method, proc, or string to call to determine if the validation should not occur (e.g. unless: :skip_validation, or unless: Proc.new { |user| user.signup_step <= 2 }). The method, proc, or string should return or evaluate to a true or false value.

• :allow_nil - Skip validation if the attribute is nil.

• :allow_blank - Skip validation if the attribute is blank.

• :strict - If the :strict option is set to true will raise ActiveModel::StrictValidationFailed instead of adding the error. :strict option can also be set to any other exception.

Example:

validates :password, presence: true, confirmation: true, if: :password_required? validates :token, length: { is: 24 }, strict: TokenLengthException 

Finally, the options :if, :unless, :on, :allow_blank, :allow_nil, :strict and :message can be given to one specific validator, as a hash:

validates :password, presence: { if: :password_required?, message: 'is forgotten.' }, confirmation: true 

# File activemodel/lib/active_model/validations/validates.rb, line 111 def validates(*attributes) defaults = attributes.extract_options!.dup validations = defaults.slice!(*_validates_default_keys) raise ArgumentError, "You need to supply at least one attribute" if attributes.empty? raise ArgumentError, "You need to supply at least one validation" if validations.empty? defaults[:attributes] = attributes validations.each do |key, options| key = "#{key.to_s.camelize}Validator" begin validator = const_get(key) rescue NameError raise ArgumentError, "Unknown validator: '#{key}'" end next unless options validates_with(validator, defaults.merge(_parse_validates_options(options))) end end

This method is used to define validations that cannot be corrected by end users and are considered exceptional. So each validator defined with bang or :strict option set to true will always raise ActiveModel::StrictValidationFailed instead of adding error when validation fails. See validates for more information about the validation itself.

class Person include ActiveModel::Validations attr_accessor :name validates! :name, presence: true end person = Person.new person.name = '' person.valid? # => ActiveModel::StrictValidationFailed: Name can't be blank 

# File activemodel/lib/active_model/validations/validates.rb, line 153 def validates!(*attributes) options = attributes.extract_options! options[:strict] = true validates(*(attributes << options)) end

Validates each attribute against a block.

class Person include ActiveModel::Validations attr_accessor :first_name, :last_name validates_each :first_name, :last_name, allow_blank: true do |record, attr, value| record.errors.add attr, "starts with z." if value.start_with?("z") end end 

Options:

• :on - Specifies the contexts where this validation is active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. on: :create or on: :custom_validation_context or on: [:create, :custom_validation_context])

• :except_on - Specifies the contexts where this validation is not active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. except: :create or except_on: :custom_validation_context or except_on: [:create, :custom_validation_context])

• :allow_nil - Skip validation if attribute is nil.

• :allow_blank - Skip validation if attribute is blank.

• :if - Specifies a method, proc, or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.

• :unless - Specifies a method, proc, or string to call to determine if the validation should not occur (e.g. unless: :skip_validation, or unless: Proc.new { |user| user.signup_step <= 2 }). The method, proc, or string should return or evaluate to a true or false value.

# File activemodel/lib/active_model/validations.rb, line 88 def validates_each(*attr_names, &block) validates_with BlockValidator, _merge_attributes(attr_names), &block end

Passes the record off to the class or classes specified and allows them to add errors based on more complex conditions.

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 

You may also pass it multiple classes, like so:

class Person include ActiveModel::Validations validates_with MyValidator, MyOtherValidator, on: :create end 

There is no default error message for validates_with. You must manually add errors to the record’s errors collection in the validator class.

To implement the validate method, you must have a record parameter defined, which is the record to be validated.

Configuration options:

• :on - Specifies the contexts where this validation is active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. on: :create or on: :custom_validation_context or on: [:create, :custom_validation_context])

• :if - Specifies a method, proc, or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc, or string should return or evaluate to a true or false value.

• :unless - Specifies a method, proc, or string to call to determine if the validation should not occur (e.g. unless: :skip_validation, or unless: Proc.new { |user| user.signup_step <= 2 }). The method, proc, or string should return or evaluate to a true or false value.

• :strict - Specifies whether validation should be strict. See ActiveModel::Validations#validates! for more information.

If you pass any additional configuration options, they will be passed to the class and available as options:

class Person include ActiveModel::Validations validates_with MyValidator, my_custom_key: 'my custom value' end class MyValidator < ActiveModel::Validator def validate(record) options[:my_custom_key] # => "my custom value" end end 

# File activemodel/lib/active_model/validations/with.rb, line 88 def validates_with(*args, &block) options = args.extract_options! options[:class] = self args.each do |klass| validator = klass.new(options.dup, &block) if validator.respond_to?(:attributes) && !validator.attributes.empty? validator.attributes.each do |attribute| _validators[attribute.to_sym] << validator end else _validators[nil] << validator end validate(validator, options) end end

List all validators that are being used to validate the model using validates_with method.

class Person include ActiveModel::Validations validates_with MyValidator validates_with OtherValidator, on: :create validates_with StrictValidator, strict: true end Person.validators # => [ # #<MyValidator:0x007fbff403e808 @options={}>, # #<OtherValidator:0x007fbff403d930 @options={on: :create}>, # #<StrictValidator:0x007fbff3204a30 @options={strict:true}> # ] 

# File activemodel/lib/active_model/validations.rb, line 204 def validators _validators.values.flatten.uniq end

List all validators that are being used to validate a specific attribute.

class Person include ActiveModel::Validations attr_accessor :name, :age validates_presence_of :name validates_inclusion_of :age, in: 0..99 end Person.validators_on(:name) # => [ # #<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>, # ] 

# File activemodel/lib/active_model/validations.rb, line 266 def validators_on(*attributes) attributes.flat_map do |attribute| _validators[attribute.to_sym] end end