# class ActiveModel::Errors

## 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, :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..

### Constants

CALLBACKS_OPTIONS
MESSAGE_OPTIONS

### Attributes

details[R]
messages[R]

### Public Class Methods

new(base) click to toggle source

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

### Public Instance Methods

[](attribute) click to toggle source

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

add(attribute, message = :invalid, options = {}) click to toggle source

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 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

added?(attribute, message = :invalid, options = {}) click to toggle source

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 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

as_json(options = nil) click to toggle source

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

blank?()
Alias for: empty?
clear() click to toggle source

Clear the error messages.

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

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

count()
Alias for: size
delete(key) click to toggle source

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

each() { |attribute, error| ... } click to toggle source

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

empty?() click to toggle source

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

Also aliased as: blank?
full_message(attribute, message) click to toggle source

Returns a full message for a given attribute.

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

    # File 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

full_messages() click to toggle source

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

Also aliased as: to_a
full_messages_for(attribute) click to toggle source

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 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

generate_message(attribute, type = :invalid, options = {}) click to toggle source

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 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

has_key?(attribute)
Alias for: include?
include?(attribute) click to toggle source

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

Also aliased as: has_key?, key?
key?(attribute)
Alias for: include?
keys() click to toggle source

Returns all message keys.

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

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

size() click to toggle source

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

Also aliased as: count
to_a()
Alias for: full_messages
to_hash(full_messages = false) click to toggle source

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 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

to_xml(options = {}) click to toggle source

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

values() click to toggle source

Returns all message values.

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

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

### Private Instance Methods

apply_default_array(hash) click to toggle source

    # File lib/active_model/errors.rb, line 459
    def apply_default_array(hash)
      hash.default_proc = proc { |h, key| h[key] = [] }
      hash
    end

normalize_detail(message, options) click to toggle source

    # File lib/active_model/errors.rb, line 449
    def normalize_detail(message, options)
      { error: message }.merge(options.except(*CALLBACKS_OPTIONS + MESSAGE_OPTIONS))
    end

normalize_message(attribute, message, options) click to toggle source

    # File lib/active_model/errors.rb, line 440
    def normalize_message(attribute, message, options)
      case message
      when Symbol
        generate_message(attribute, message, options.except(*CALLBACKS_OPTIONS))
      else
        message
      end
    end

without_default_proc(hash) click to toggle source

    # File lib/active_model/errors.rb, line 453
    def without_default_proc(hash)
      hash.dup.tap do |new_h|
        new_h.default_proc = nil
      end
    end