# File activemodel/lib/active_model/errors.rb, line 70
def initialize(base)
  @base     = base
  @messages = {}
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 135
def [](attribute)
  get(attribute.to_sym) || set(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"]

# File activemodel/lib/active_model/errors.rb, line 143
def []=(attribute, error)
  self[attribute] << error
end

Adds to the supplied attribute the supplied error message.

person.errors[:name] = "must be set"
person.errors[:name] # => ['must be set']

# File activemodel/lib/active_model/errors.rb, line 298
def add(attribute, message = :invalid, options = {})
  message = normalize_message(attribute, message, options)
  if exception = options[:strict]
    exception = ActiveModel::StrictValidationFailed if exception == true
    raise exception, full_message(attribute, message)
  end

  self[attribute] << message
end

Adds message to the error messages 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, 'must be implemented')
# => ["is invalid", "must be implemented"]

person.errors.messages
# => {:name=>["must be implemented", "is 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, nil, strict: true)
# => ActiveModel::StrictValidationFailed: name is invalid
person.errors.add(:name, nil, 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, "either name or email must be present")
person.errors.messages
# => {:base=>["either name or email must be present"]}

# File activemodel/lib/active_model/errors.rb, line 328
def add_on_blank(attributes, options = {})
  Array(attributes).each do |attribute|
    value = @base.send(:read_attribute_for_validation, attribute)
    add(attribute, :blank, options) if value.blank?
  end
end

Will add an error message to each of the attributes in attributes that is blank (using Object#blank?).

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

# File activemodel/lib/active_model/errors.rb, line 314
def add_on_empty(attributes, options = {})
  Array(attributes).each do |attribute|
    value = @base.send(:read_attribute_for_validation, attribute)
    is_empty = value.respond_to?(:empty?) ? value.empty? : false
    add(attribute, :empty, options) if value.nil? || is_empty
  end
end

Will add an error message to each of the attributes in attributes that is empty.

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

# File activemodel/lib/active_model/errors.rb, line 340
def added?(attribute, message = :invalid, options = {})
  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, false otherwise. message is treated the same as for add.

person.errors.add :name, :blank
person.errors.added? :name, :blank # => true

# File activemodel/lib/active_model/errors.rb, line 244
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 85
def clear
  messages.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 208
def count
  to_a.size
end

Returns the number of error messages.

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

# File activemodel/lib/active_model/errors.rb, line 126
def delete(key)
  messages.delete(key)
end

Delete messages for key. Returns the deleted messages.

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

# File activemodel/lib/active_model/errors.rb, line 161
def each
  messages.each_key do |attribute|
    self[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, "can't be blank")
person.errors.each do |attribute, error|
  # Will yield :name and "can't be blank"
end

person.errors.add(:name, "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 217
def empty?
  all? { |k, v| v && v.empty? && !v.is_a?(String) }
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 376
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 355
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 369
def full_messages_for(attribute)
  (get(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 411
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 << options.delete(:message)
  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
  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
  }.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 models.MODEL.attributes.ATTRIBUTE.MESSAGE, if it's not there, it's looked up in 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 108
def get(key)
  messages[key]
end

Get messages for key.

person.errors.messages   # => {:name=>["cannot be nil"]}
person.errors.get(:name) # => ["cannot be nil"]
person.errors.get(:age)  # => nil

# File activemodel/lib/active_model/errors.rb, line 95
def include?(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 189
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 117
def set(key, value)
  messages[key] = value
end

Set messages for key to value.

person.errors.get(:name) # => ["cannot be nil"]
person.errors.set(:name, ["can't be nil"])
person.errors.get(:name) # => ["can't be nil"]

# File activemodel/lib/active_model/errors.rb, line 173
def size
  values.flatten.size
end

Returns the number of error messages.

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

# File activemodel/lib/active_model/errors.rb, line 198
def to_a
  full_messages
end

Returns an array of error messages, with the attribute name included.

person.errors.add(:name, "can't be blank")
person.errors.add(:name, "must be specified")
person.errors.to_a # => ["name can't be blank", "name must be specified"]

# File activemodel/lib/active_model/errors.rb, line 253
def to_hash(full_messages = false)
  if full_messages
    self.messages.each_with_object({}) do |(attribute, array), messages|
      messages[attribute] = array.map { |message| full_message(attribute, message) }
    end
  else
    self.messages.dup
  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 234
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, "can't be blank")
person.errors.add(:name, "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 181
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"]]