Active Model Validations

Provides a full validation framework to your objects.

A minimal implementation could be:

class Person
  include ActiveModel::Validations

  attr_accessor :first_name, :last_name

  validates_each :first_name, :last_name do |record, attr, value|
    record.errors.add attr, "starts with z." if value.start_with?("z")
  end
end

Which provides you with the full standard validation stack that you know from Active Record:

person = Person.new
person.valid?                   # => true
person.invalid?                 # => false

person.first_name = 'zoolander'
person.valid?                   # => false
person.invalid?                 # => true
person.errors.messages          # => {first_name:["starts with z."]}

Note that ActiveModel::Validations automatically adds an errors method to your instances initialized with a new ActiveModel::Errors object, so there is no need for you to do this manually.

Namespace

Module

Class

ActiveModel::Validations::AcceptanceValidator

Included Modules

ActiveModel::Validations::HelperMethods

Instance Public methods

errors()

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

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates_presence_of :name
end

person = Person.new
person.valid? # => false
person.errors # => #<ActiveModel::Errors:0x007fe603816640 @messages={name:["can't be blank"]}>

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 328
    def errors
      @errors ||= Errors.new(self)
    end

🔎 See on GitHub

freeze()

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 372
    def freeze
      errors
      context_for_validation

      super
    end

🔎 See on GitHub

invalid?(context = nil)

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

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates_presence_of :name
end

person = Person.new
person.name = ''
person.invalid? # => true
person.name = 'david'
person.invalid? # => false

Context can optionally be supplied to define which callbacks to test against (the context is defined on the validations using :on).

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates_presence_of :name, on: :new
end

person = Person.new
person.invalid?       # => false
person.invalid?(:new) # => true

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 408
    def invalid?(context = nil)
      !valid?(context)
    end

🔎 See on GitHub

valid?(context = nil)

Runs all the specified validations and returns true if no errors were added otherwise false.

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates_presence_of :name
end

person = Person.new
person.name = ''
person.valid? # => false
person.name = 'david'
person.valid? # => true

Context can optionally be supplied to define which callbacks to test against (the context is defined on the validations using :on).

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates_presence_of :name, on: :new
end

person = Person.new
person.valid?       # => true
person.valid?(:new) # => false

Also aliased as: validate

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 361
    def valid?(context = nil)
      current_context = validation_context
      context_for_validation.context = context
      errors.clear
      run_validations!
    ensure
      context_for_validation.context = current_context
    end

🔎 See on GitHub

validate(context = nil)

Alias for: valid?

validate!(context = nil)

Runs all the validations within the specified context. Returns true if no errors are found, raises ValidationError otherwise.

Validations with no :on option will run no matter the context. Validations with some :on option will only run in the specified context.

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 417
    def validate!(context = nil)
      valid?(context) || raise_validation_error
    end

🔎 See on GitHub

validates_with(*args, &block)

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

  validate :instance_validations

  def instance_validations
    validates_with MyValidator
  end
end

Please consult the class method documentation for more information on creating your own validator.

You may also pass it multiple classes, like so:

class Person
  include ActiveModel::Validations

  validate :instance_validations, on: :create

  def instance_validations
    validates_with MyValidator, MyOtherValidator
  end
end

Standard configuration options (:on, :if and :unless), which are available on the class version of validates_with, should instead be placed on the validates method as these are applied and tested in the callback.

If you pass any additional configuration options, they will be passed to the class and available as options, please refer to the class version of this method for more information.

📝 Source code

# File activemodel/lib/active_model/validations/with.rb, line 144
    def validates_with(*args, &block)
      options = args.extract_options!
      options[:class] = self.class

      args.each do |klass|
        validator = klass.new(options.dup, &block)
        validator.validate(self)
      end
    end

🔎 See on GitHub

validation_context()

Returns the context when running validations.

This is useful when running validations except a certain context (opposite to the on option).

class Person
  include ActiveModel::Validations

  attr_accessor :name
  validates :name, presence: true, if: -> { validation_context != :custom }
end

person = Person.new
person.valid?          #=> false
person.valid?(:new)    #=> false
person.valid?(:custom) #=> true

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 454
    def validation_context
      context_for_validation.context
    end

🔎 See on GitHub

Instance Private methods

raise_validation_error()

📝 Source code

# File activemodel/lib/active_model/validations.rb, line 478
    def raise_validation_error # :doc:
      raise(ValidationError.new(self))
    end

🔎 See on GitHub