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Active Model Errors

Provides a modified Hash that 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, "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 Person.human_attribute_name(attr, options = {})
    attr
  end

  def Person.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
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Included Modules
Constants
CALLBACKS_OPTIONS = [:if, :unless, :on, :allow_nil, :allow_blank, :strict]
 
Attributes
[R] messages
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
# File activemodel/lib/active_model/errors.rb, line 70
def initialize(base)
  @base     = base
  @messages = {}
end
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"]
# File activemodel/lib/active_model/errors.rb, line 133
def [](attribute)
  get(attribute.to_sym) || set(attribute.to_sym, [])
end
[]=(attribute, error)

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 141
def []=(attribute, error)
  self[attribute] << error
end
add(attribute, message = :invalid, options = {})

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 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
add_on_blank(attributes, options = {})

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 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
add_on_empty(attributes, options = {})

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

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 340
def added?(attribute, message = :invalid, options = {})
  message = normalize_message(attribute, message, options)
  self[attribute].include? message
end
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"]}
# File activemodel/lib/active_model/errors.rb, line 242
def as_json(options=nil)
  to_hash(options && options[:full_messages])
end
blank?()

aliases empty?

Alias for: empty?
clear()

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 85
def clear
  messages.clear
end
count()

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 206
def count
  to_a.size
end
delete(key)

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 124
def delete(key)
  messages.delete(key)
end
each()

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 159
def each
  messages.each_key do |attribute|
    self[attribute].each { |error| yield attribute, error }
  end
end
empty?()

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
Also aliased as: blank?
# File activemodel/lib/active_model/errors.rb, line 215
def empty?
  all? { |k, v| v && v.empty? && !v.is_a?(String) }
end
full_message(attribute, message)

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 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
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"]
# File activemodel/lib/active_model/errors.rb, line 355
def full_messages
  map { |attribute, message| full_message(attribute, message) }
end
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"]
# File activemodel/lib/active_model/errors.rb, line 369
def full_messages_for(attribute)
  (get(attribute) || []).map { |message| full_message(attribute, message) }
end
generate_message(attribute, type = :invalid, options = {})

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 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.class.model_name.human,
    attribute: @base.class.human_attribute_name(attribute),
    value: value
  }.merge!(options)

  I18n.translate(key, options)
end
get(key)

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 106
def get(key)
  messages[key]
end
has_key?(attribute)

aliases include?

Alias for: include?
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?
# File activemodel/lib/active_model/errors.rb, line 95
def include?(attribute)
  messages[attribute].present?
end
keys()

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 187
def keys
  messages.keys
end
set(key, value)

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 115
def set(key, value)
  messages[key] = value
end
size()

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 171
def size
  values.flatten.size
end
to_a()

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 196
def to_a
  full_messages
end
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"]}
# File activemodel/lib/active_model/errors.rb, line 251
def to_hash(full_messages = false)
  if full_messages
    messages = {}
    self.messages.each do |attribute, array|
      messages[attribute] = array.map { |message| full_message(attribute, message) }
    end
    messages
  else
    self.messages.dup
  end
end
to_xml(options={})

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 232
def to_xml(options={})
  to_a.to_xml({ root: "errors", skip_types: true }.merge!(options))
end
values()

Returns all message values.

person.errors.messages # => {:name=>["cannot be nil", "must be specified"]}
person.errors.values   # => [["cannot be nil", "must be specified"]]
# File activemodel/lib/active_model/errors.rb, line 179
def values
  messages.values
end