Active Model Errors

Provides error related functionalities you can include in your object for handling error messages and interacting with Action View helpers.

A minimal implementation could be:

class Person
  # Required dependency for ActiveModel::Errors
  extend ActiveModel::Naming

  def initialize
    @errors = ActiveModel::Errors.new(self)
  end

  attr_accessor :name
  attr_reader   :errors

  def validate!
    errors.add(:name, :blank, message: "cannot be nil") if name.nil?
  end

  # The following methods are needed to be minimally implemented

  def read_attribute_for_validation(attr)
    send(attr)
  end

  def self.human_attribute_name(attr, options = {})
    attr
  end

  def self.lookup_ancestors
    [self]
  end
end

The last three methods are required in your object for Errors to be able to generate error messages correctly and also handle multiple languages. Of course, if you extend your object with ActiveModel::Translation you will not need to implement the last two. Likewise, using ActiveModel::Validations will handle the validation related methods for you.

The above allows you to do:

person = Person.new
person.validate!            # => ["cannot be nil"]
person.errors.full_messages # => ["name cannot be nil"]
# etc..

Methods

Included Modules

Attributes

[R] errors

The actual array of Error objects This method is aliased to objects.

[R] objects

The actual array of Error objects This method is aliased to objects.

Class Public methods

new(base)

Pass in the instance of the object that is using the errors object.

class Person
  def initialize
    @errors = ActiveModel::Errors.new(self)
  end
end
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 117
    def initialize(base)
      @base = base
      @errors = []
    end
πŸ”Ž See on GitHub

Instance Public methods

[](attribute)

When passed a symbol or a name of a method, returns an array of errors for the method.

person.errors[:name]  # => ["cannot be nil"]
person.errors['name'] # => ["cannot be nil"]
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 229
    def [](attribute)
      messages_for(attribute)
    end
πŸ”Ž See on GitHub

add(attribute, type = :invalid, **options)

Adds a new error of type on attribute. More than one error can be added to the same attribute. If no type is supplied, :invalid is assumed.

person.errors.add(:name)
# Adds <#ActiveModel::Error attribute=name, type=invalid>
person.errors.add(:name, :not_implemented, message: "must be implemented")
# Adds <#ActiveModel::Error attribute=name, type=not_implemented,
                            options={:message=>"must be implemented"}>

person.errors.messages
# => {:name=>["is invalid", "must be implemented"]}

If type is a string, it will be used as error message.

If type is a symbol, it will be translated using the appropriate scope (see generate_message).

person.errors.add(:name, :blank)
person.errors.messages
# => {:name=>["can't be blank"]}

person.errors.add(:name, :too_long, count: 25)
person.errors.messages
# => ["is too long (maximum is 25 characters)"]

If type is a proc, it will be called, allowing for things like Time.now to be used within an error.

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

person.errors.add(:name, :invalid, strict: true)
# => ActiveModel::StrictValidationFailed: Name is invalid
person.errors.add(:name, :invalid, strict: NameIsInvalid)
# => NameIsInvalid: Name is invalid

person.errors.messages # => {}

attribute should be set to :base if the error is not directly associated with a single attribute.

person.errors.add(:base, :name_or_email_blank,
  message: "either name or email must be present")
person.errors.messages
# => {:base=>["either name or email must be present"]}
person.errors.details
# => {:base=>[{error: :name_or_email_blank}]}
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 342
    def add(attribute, type = :invalid, **options)
      attribute, type, options = normalize_arguments(attribute, type, **options)
      error = Error.new(@base, attribute, type, **options)

      if exception = options[:strict]
        exception = ActiveModel::StrictValidationFailed if exception == true
        raise exception, error.full_message
      end

      @errors.append(error)

      error
    end
πŸ”Ž See on GitHub

added?(attribute, type = :invalid, options = {})

Returns true if an error matches provided attribute and type, or false otherwise. type is treated the same as for add.

person.errors.add :name, :blank
person.errors.added? :name, :blank           # => true
person.errors.added? :name, "can't be blank" # => true

If the error requires options, then it returns true with the correct options, or false with incorrect or missing options.

person.errors.add :name, :too_long, count: 25
person.errors.added? :name, :too_long, count: 25                     # => true
person.errors.added? :name, "is too long (maximum is 25 characters)" # => true
person.errors.added? :name, :too_long, count: 24                     # => false
person.errors.added? :name, :too_long                                # => false
person.errors.added? :name, "is too long"                            # => false
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 372
    def added?(attribute, type = :invalid, options = {})
      attribute, type, options = normalize_arguments(attribute, type, **options)

      if type.is_a? Symbol
        @errors.any? { |error|
          error.strict_match?(attribute, type, **options)
        }
      else
        messages_for(attribute).include?(type)
      end
    end
πŸ”Ž See on GitHub

as_json(options = nil)

Returns a Hash that can be used as the JSON representation for this object. You can pass the :full_messages option. This determines if the JSON object should contain full messages or not (false by default).

person.errors.as_json                      # => {:name=>["cannot be nil"]}
person.errors.as_json(full_messages: true) # => {:name=>["name cannot be nil"]}
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 247
    def as_json(options = nil)
      to_hash(options && options[:full_messages])
    end
πŸ”Ž See on GitHub

attribute_names()

Returns all error attribute names

person.errors.messages        # => {:name=>["cannot be nil", "must be specified"]}
person.errors.attribute_names # => [:name]
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 237
    def attribute_names
      @errors.map(&:attribute).uniq.freeze
    end
πŸ”Ž See on GitHub

clear

Clears all errors. Clearing the errors does not, however, make the model valid. The next time the validations are run (for example, via ActiveRecord::Validations#valid?), the errors collection will be filled again if any validations fail.

πŸ”Ž See on GitHub

delete(attribute, type = nil, **options)

Delete messages for key. Returns the deleted messages.

person.errors[:name]        # => ["cannot be nil"]
person.errors.delete(:name) # => ["cannot be nil"]
person.errors[:name]        # => []
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 215
    def delete(attribute, type = nil, **options)
      attribute, type, options = normalize_arguments(attribute, type, **options)
      matches = where(attribute, type, **options)
      matches.each do |error|
        @errors.delete(error)
      end
      matches.map(&:message).presence
    end
πŸ”Ž See on GitHub

details()

Returns a Hash of attributes with an array of their error details.

πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 276
    def details
      hash = group_by_attribute.transform_values do |errors|
        errors.map(&:details)
      end
      hash.default = EMPTY_ARRAY
      hash.freeze
      hash
    end
πŸ”Ž See on GitHub

each(&block)

Iterates through each error object.

person.errors.add(:name, :too_short, count: 2)
person.errors.each do |error|
  # Will yield <#ActiveModel::Error attribute=name, type=too_short,
                                    options={:count=>3}>
end
πŸ”Ž See on GitHub

empty?

Returns true if there are no errors.

πŸ”Ž See on GitHub

full_message(attribute, message)

Returns a full message for a given attribute.

person.errors.full_message(:name, 'is invalid') # => "Name is invalid"
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 451
    def full_message(attribute, message)
      Error.full_message(attribute, message, @base)
    end
πŸ”Ž See on GitHub

full_messages()

Returns all the full error messages in an array.

class Person
  validates_presence_of :name, :address, :email
  validates_length_of :name, in: 5..30
end

person = Person.create(address: '123 First St.')
person.errors.full_messages
# => ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Email can't be blank"]
Also aliased as: to_a
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 415
    def full_messages
      @errors.map(&:full_message)
    end
πŸ”Ž See on GitHub

full_messages_for(attribute)

Returns all the full error messages for a given attribute in an array.

class Person
  validates_presence_of :name, :email
  validates_length_of :name, in: 5..30
end

person = Person.create()
person.errors.full_messages_for(:name)
# => ["Name is too short (minimum is 5 characters)", "Name can't be blank"]
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 430
    def full_messages_for(attribute)
      where(attribute).map(&:full_message).freeze
    end
πŸ”Ž See on GitHub

generate_message(attribute, type = :invalid, options = {})

Translates an error message in its default scope (activemodel.errors.messages).

Error messages are first looked up in activemodel.errors.models.MODEL.attributes.ATTRIBUTE.MESSAGE, if it’s not there, it’s looked up in activemodel.errors.models.MODEL.MESSAGE and if that is not there also, it returns the translation of the default message (e.g. activemodel.errors.messages.MESSAGE). The translated model name, translated attribute name, and the value are available for interpolation.

When using inheritance in your models, it will check all the inherited models too, but only if the model itself hasn’t been found. Say you have class Admin < User; end and you wanted the translation for the :blank error message for the title attribute, it looks for these translations:

  • activemodel.errors.models.admin.attributes.title.blank

  • activemodel.errors.models.admin.blank

  • activemodel.errors.models.user.attributes.title.blank

  • activemodel.errors.models.user.blank

  • any default you provided through the options hash (in the activemodel.errors scope)

  • activemodel.errors.messages.blank

  • errors.attributes.title.blank

  • errors.messages.blank

πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 479
    def generate_message(attribute, type = :invalid, options = {})
      Error.generate_message(attribute, type, @base, options)
    end
πŸ”Ž See on GitHub

group_by_attribute()

Returns a Hash of attributes with an array of their Error objects.

person.errors.group_by_attribute
# => {:name=>[<#ActiveModel::Error>, <#ActiveModel::Error>]}
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 289
    def group_by_attribute
      @errors.group_by(&:attribute)
    end
πŸ”Ž See on GitHub

has_key?(attribute)

Alias for: include?

import(error, override_options = {})

Imports one error. Imported errors are wrapped as a NestedError, providing access to original error object. If attribute or type needs to be overridden, use override_options.

Options

  • :attribute - Override the attribute the error belongs to.

  • :type - Override type of the error.

πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 154
    def import(error, override_options = {})
      [:attribute, :type].each do |key|
        if override_options.key?(key)
          override_options[key] = override_options[key].to_sym
        end
      end
      @errors.append(NestedError.new(@base, error, override_options))
    end
πŸ”Ž See on GitHub

include?(attribute)

Returns true if the error messages include an error for the given key attribute, false otherwise.

person.errors.messages        # => {:name=>["cannot be nil"]}
person.errors.include?(:name) # => true
person.errors.include?(:age)  # => false
Also aliased as: has_key?, key?
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 202
    def include?(attribute)
      @errors.any? { |error|
        error.match?(attribute.to_sym)
      }
    end
πŸ”Ž See on GitHub

key?(attribute)

Alias for: include?

merge!(other)

Merges the errors from other, each Error wrapped as NestedError.

Parameters

Examples

person.errors.merge!(other)
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 174
    def merge!(other)
      return errors if equal?(other)

      other.errors.each { |error|
        import(error)
      }
    end
πŸ”Ž See on GitHub

messages()

Returns a Hash of attributes with an array of their error messages.

πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 268
    def messages
      hash = to_hash
      hash.default = EMPTY_ARRAY
      hash.freeze
      hash
    end
πŸ”Ž See on GitHub

messages_for(attribute)

Returns all the error messages for a given attribute in an array.

class Person
  validates_presence_of :name, :email
  validates_length_of :name, in: 5..30
end

person = Person.create()
person.errors.messages_for(:name)
# => ["is too short (minimum is 5 characters)", "can't be blank"]
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 444
    def messages_for(attribute)
      where(attribute).map(&:message)
    end
πŸ”Ž See on GitHub

of_kind?(attribute, type = :invalid)

Returns true if an error on the attribute with the given type is present, or false otherwise. type is treated the same as for add.

person.errors.add :age
person.errors.add :name, :too_long, count: 25
person.errors.of_kind? :age                                            # => true
person.errors.of_kind? :name                                           # => false
person.errors.of_kind? :name, :too_long                                # => true
person.errors.of_kind? :name, "is too long (maximum is 25 characters)" # => true
person.errors.of_kind? :name, :not_too_long                            # => false
person.errors.of_kind? :name, "is too long"                            # => false
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 395
    def of_kind?(attribute, type = :invalid)
      attribute, type = normalize_arguments(attribute, type)

      if type.is_a? Symbol
        !where(attribute, type).empty?
      else
        messages_for(attribute).include?(type)
      end
    end
πŸ”Ž See on GitHub

size

Returns number of errors.

πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 103
    def_delegators :@errors, :each, :clear, :empty?, :size, :uniq!
πŸ”Ž See on GitHub

to_a()

Alias for: full_messages

to_hash(full_messages = false)

Returns a Hash of attributes with their error messages. If full_messages is true, it will contain full messages (see full_message).

person.errors.to_hash       # => {:name=>["cannot be nil"]}
person.errors.to_hash(true) # => {:name=>["name cannot be nil"]}
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 256
    def to_hash(full_messages = false)
      message_method = full_messages ? :full_message : :message
      group_by_attribute.transform_values do |errors|
        errors.map(&message_method)
      end
    end
πŸ”Ž See on GitHub

where(attribute, type = nil, **options)

Search for errors matching attribute, type, or options.

Only supplied params will be matched.

person.errors.where(:name) # => all name errors.
person.errors.where(:name, :too_short) # => all name errors being too short
person.errors.where(:name, :too_short, minimum: 2) # => all name errors being too short and minimum is 2
πŸ“ Source code
# File activemodel/lib/active_model/errors.rb, line 189
    def where(attribute, type = nil, **options)
      attribute, type, options = normalize_arguments(attribute, type, **options)
      @errors.select { |error|
        error.match?(attribute, type, **options)
      }
    end
πŸ”Ž See on GitHub