class ActiveModel::Errors

# File activemodel/lib/active_model/errors.rb, line 72
def initialize(base)
  @base     = base
  @messages = apply_default_array({})
  @details = apply_default_array({})
end

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

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

# File activemodel/lib/active_model/errors.rb, line 144
def [](attribute)
  messages[attribute.to_sym]
end

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"]

Note that, if you try to get errors of an attribute which has no errors associated with it, this method will instantiate an empty error list for it and keys will return an array of error keys which includes this attribute.

person.errors.keys    # => []
person.errors[:name]  # => []
person.errors.keys    # => [:name]

# File activemodel/lib/active_model/errors.rb, line 286
def add(attribute, message = :invalid, options = {})
  message = message.call if message.respond_to?(:call)
  detail  = normalize_detail(message, options)
  message = normalize_message(attribute, message, options)
  if exception = options[:strict]
    exception = ActiveModel::StrictValidationFailed if exception == true
    raise exception, full_message(attribute, message)
  end

  details[attribute.to_sym]  << detail
  messages[attribute.to_sym] << message
end

Adds message to the error messages and used validator type to details on attribute. More than one error can be added to the same attribute. If no message is supplied, :invalid is assumed.

person.errors.add(:name)
# => ["is invalid"]
person.errors.add(:name, :not_implemented, message: "must be implemented")
# => ["is invalid", "must be implemented"]

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

person.errors.details
# => {:name=>[{error: :not_implemented}, {error: :invalid}]}

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

If message 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}]}

# File activemodel/lib/active_model/errors.rb, line 315
def added?(attribute, message = :invalid, options = {})
  message = message.call if message.respond_to?(:call)
  message = normalize_message(attribute, message, options)
  self[attribute].include? message
end

Returns true if an error on the attribute with the given message is present, or false otherwise. message 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 message requires an option, then it returns true with the correct option, or false with an incorrect or missing option.

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

# File activemodel/lib/active_model/errors.rb, line 226
def as_json(options = nil)
  to_hash(options && options[:full_messages])
end

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"]}

# File activemodel/lib/active_model/errors.rb, line 101
def clear
  messages.clear
  details.clear
end

Clear the error messages.

person.errors.full_messages # => ["name cannot be nil"]
person.errors.clear
person.errors.full_messages # => []

# File activemodel/lib/active_model/errors.rb, line 124
def delete(key)
  attribute = key.to_sym
  details.delete(attribute)
  messages.delete(attribute)
end

Delete messages for key. Returns the deleted messages.

person.errors[:name]        # => ["cannot be nil"]
person.errors.delete(:name) # => ["cannot be nil"]
person.errors[:name]        # => []

# File activemodel/lib/active_model/errors.rb, line 162
def each
  messages.each_key do |attribute|
    messages[attribute].each { |error| yield attribute, error }
  end
end

Iterates through each error key, value pair in the error messages hash. Yields the attribute and the error for that attribute. If the attribute has more than one error message, yields once for each error message.

person.errors.add(:name, :blank, message: "can't be blank")
person.errors.each do |attribute, error|
  # Will yield :name and "can't be blank"
end

person.errors.add(:name, :not_specified, message: "must be specified")
person.errors.each do |attribute, error|
  # Will yield :name and "can't be blank"
  # then yield :name and "must be specified"
end

# File activemodel/lib/active_model/errors.rb, line 200
def empty?
  size.zero?
end

Returns true if no errors are found, false otherwise. If the error message is a string it can be empty.

person.errors.full_messages # => ["name cannot be nil"]
person.errors.empty?        # => false

# File activemodel/lib/active_model/errors.rb, line 354
def full_message(attribute, message)
  return message if attribute == :base
  attr_name = attribute.to_s.tr(".", "_").humanize
  attr_name = @base.class.human_attribute_name(attribute, default: attr_name)
  I18n.t(:"errors.format",
    default:  "%{attribute} %{message}",
    attribute: attr_name,
    message:   message)
end

Returns a full message for a given attribute.

person.errors.full_message(:name, 'is invalid') # => "Name is invalid"

# File activemodel/lib/active_model/errors.rb, line 331
def full_messages
  map { |attribute, message| full_message(attribute, message) }
end

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"]

# File activemodel/lib/active_model/errors.rb, line 346
def full_messages_for(attribute)
  attribute = attribute.to_sym
  messages[attribute].map { |message| full_message(attribute, message) }
end

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"]

# File activemodel/lib/active_model/errors.rb, line 388
def generate_message(attribute, type = :invalid, options = {})
  type = options.delete(:message) if options[:message].is_a?(Symbol)

  if @base.class.respond_to?(:i18n_scope)
    defaults = @base.class.lookup_ancestors.map do |klass|
      [ :"#{@base.class.i18n_scope}.errors.models.#{klass.model_name.i18n_key}.attributes.#{attribute}.#{type}",
        :"#{@base.class.i18n_scope}.errors.models.#{klass.model_name.i18n_key}.#{type}" ]
    end
  else
    defaults = []
  end

  defaults << :"#{@base.class.i18n_scope}.errors.messages.#{type}" if @base.class.respond_to?(:i18n_scope)
  defaults << :"errors.attributes.#{attribute}.#{type}"
  defaults << :"errors.messages.#{type}"

  defaults.compact!
  defaults.flatten!

  key = defaults.shift
  defaults = options.delete(:message) if options[:message]
  value = (attribute != :base ? @base.send(:read_attribute_for_validation, attribute) : nil)

  options = {
    default: defaults,
    model: @base.model_name.human,
    attribute: @base.class.human_attribute_name(attribute),
    value: value,
    object: @base
  }.merge!(options)

  I18n.translate(key, options)
end

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

# File activemodel/lib/active_model/errors.rb, line 112
def include?(attribute)
  attribute = attribute.to_sym
  messages.key?(attribute) && messages[attribute].present?
end

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

# File activemodel/lib/active_model/errors.rb, line 191
def keys
  messages.keys
end

Returns all message keys.

person.errors.messages # => {:name=>["cannot be nil", "must be specified"]}
person.errors.keys     # => [:name]

# File activemodel/lib/active_model/errors.rb, line 174
def size
  values.flatten.size
end

Returns the number of error messages.

person.errors.add(:name, :blank, message: "can't be blank")
person.errors.size # => 1
person.errors.add(:name, :not_specified, message: "must be specified")
person.errors.size # => 2

# File activemodel/lib/active_model/errors.rb, line 235
def to_hash(full_messages = false)
  if full_messages
    messages.each_with_object({}) do |(attribute, array), messages|
      messages[attribute] = array.map { |message| full_message(attribute, message) }
    end
  else
    without_default_proc(messages)
  end
end

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"]}

# File activemodel/lib/active_model/errors.rb, line 216
def to_xml(options = {})
  to_a.to_xml({ root: "errors", skip_types: true }.merge!(options))
end

Returns an xml formatted representation of the Errors hash.

person.errors.add(:name, :blank, message: "can't be blank")
person.errors.add(:name, :not_specified, message: "must be specified")
person.errors.to_xml
# =>
#  <?xml version=\"1.0\" encoding=\"UTF-8\"?>
#  <errors>
#    <error>name can't be blank</error>
#    <error>name must be specified</error>
#  </errors>

# File activemodel/lib/active_model/errors.rb, line 183
def values
  messages.values
end

Returns all message values.

person.errors.messages # => {:name=>["cannot be nil", "must be specified"]}
person.errors.values   # => [["cannot be nil", "must be specified"]]