Class: ActiveModel::Errors
| Relationships & Source Files | |
| Super Chains via Extension / Inclusion / Inheritance | |
| Instance Chain: 
          self,
           ::Enumerable | |
| Inherits: | Object | 
| Defined in: | activemodel/lib/active_model/errors.rb | 
Overview
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,  = {})
    attr
  end
  def self.lookup_ancestors
    [self]
  end
endThe 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 Translation you will not need to implement the last two. Likewise, using 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. # => ["name cannot be nil"]
# etc..Constant Summary
- 
    CALLBACKS_OPTIONS =
    
 # File 'activemodel/lib/active_model/errors.rb', line 62[:if, :unless, :on, :allow_nil, :allow_blank, :strict] 
- 
    MESSAGE_OPTIONS =
    
 # File 'activemodel/lib/active_model/errors.rb', line 63[:] 
Class Method Summary
- 
    
      .new(base)  ⇒ Errors 
    
    constructor
    Pass in the instance of the object that is using the errors object. 
Instance Attribute Summary
- 
    
      #blank?  
    
    readonly
    Alias for #empty?. 
- #details readonly
- 
    
      #empty?  ⇒ Boolean 
      (also: #blank?)
    
    readonly
    Returns trueif no errors are found,falseotherwise.
- #messages readonly
::Enumerable - Included
| #many? | Returns  | 
Instance Method Summary
- 
    
      #[](attribute)  
    
    When passed a symbol or a name of a method, returns an array of errors for the method. 
- 
    
      #add(attribute, message = :invalid, options = {})  
    
    Adds messageto the error messages and used validator type to #details onattribute.
- 
    
      #added?(attribute, message = :invalid, options = {})  ⇒ Boolean 
    
    Returns trueif an error on the attribute with the given message is present, orfalseotherwise.
- 
    
      #as_json(options = nil)  
    
    Returns a ::Hashthat can be used as the JSON representation for this object.
- 
    
      #clear  
    
    Clear the error messages. 
- 
    
      #count  
    
    Alias for #size. 
- 
    
      #delete(key)  
    
    Delete messages for key.
- 
    
      #each  
    
    Iterates through each error key, value pair in the error messages hash. 
- 
    
      #full_message(attribute, message)  
    
    Returns a full message for a given attribute. 
- 
    
      #full_messages  
      (also: #to_a)
    
    Returns all the full error messages in an array. 
- 
    
      #full_messages_for(attribute)  
    
    Returns all the full error messages for a given attribute in an array. 
- 
    
      #generate_message(attribute, type = :invalid, options = {})  
    
    Translates an error message in its default scope ( activemodel.errors.messages).
- 
    
      #has_key?(attribute)  
    
    Alias for #include?. 
- 
    
      #include?(attribute)  ⇒ Boolean 
      (also: #has_key?, #key?)
    
    Returns trueif the error messages include an error for the given keyattribute,falseotherwise.
- 
    
      #key?(attribute)  
    
    Alias for #include?. 
- 
    
      #keys  
    
    Returns all message keys. 
- 
    
      #merge!(other)  
    
    Merges the errors from other.
- 
    
      #size  
      (also: #count)
    
    Returns the number of error messages. 
- 
    
      #to_a  
    
    Alias for #full_messages. 
- 
    
      #to_hash(full_messages = false)  
    
    Returns a ::Hashof attributes with their error messages.
- 
    
      #to_xml(options = {})  
    
    Returns an xml formatted representation of the Errorshash.
- 
    
      #values  
    
    Returns all message values. 
::Enumerable - Included
Constructor Details
    .new(base)  ⇒ Errors 
  
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 74
def initialize(base) @base = base @messages = apply_default_array({}) @details = apply_default_array({}) end
Instance Attribute Details
#blank? (readonly)
Alias for #empty?.
# File 'activemodel/lib/active_model/errors.rb', line 212
alias :blank? :empty?
#details (readonly)
[ GitHub ]# File 'activemodel/lib/active_model/errors.rb', line 65
attr_reader :, :details
    #empty?  ⇒ Boolean  (readonly)
    Also known as: #blank?
  
Returns true if no errors are found, false otherwise. If the error message is a string it can be empty.
person.errors. # => ["name cannot be nil"]
person.errors.empty?        # => false# File 'activemodel/lib/active_model/errors.rb', line 209
def empty? size.zero? end
#messages (readonly)
[ GitHub ]# File 'activemodel/lib/active_model/errors.rb', line 65
attr_reader :, :details
Instance Method Details
#[](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 149
def [](attribute) [attribute.to_sym] end
#add(attribute, message = :invalid, options = {})
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.
# => {: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 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. # => {}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.
# => {: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 295
def add(attribute, = :invalid, = {}) = .call if .respond_to?(:call) detail = normalize_detail(, ) = (attribute, , ) if exception = [:strict] exception = ActiveModel::StrictValidationFailed if exception == true raise exception, (attribute, ) end details[attribute.to_sym] << detail [attribute.to_sym] << end
    #added?(attribute, message = :invalid, options = {})  ⇒ Boolean 
  
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" # => trueIf 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#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 235
def as_json( = nil) to_hash( && [:]) end
#clear
Clear the error messages.
person.errors. # => ["name cannot be nil"]
person.errors.clear
person.errors. # => []# File 'activemodel/lib/active_model/errors.rb', line 115
def clear .clear details.clear end
#count
Alias for #size.
# File 'activemodel/lib/active_model/errors.rb', line 182
alias :count :size
#delete(key)
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 138
def delete(key) attribute = key.to_sym details.delete(attribute) .delete(attribute) 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, :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 167
def each .each_key do |attribute| [attribute].each { |error| yield attribute, error } end end
#full_message(attribute, message)
Returns a full message for a given attribute.
person.errors.(:name, 'is invalid') # => "Name is invalid"# File 'activemodel/lib/active_model/errors.rb', line 367
def (attribute, ) return 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: ) end
#full_messages Also known as: #to_a
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.
# => ["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 344
def map { |attribute, | (attribute, ) } 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.(:name)
# => ["Name is too short (minimum is 5 characters)", "Name can't be blank"]# File 'activemodel/lib/active_model/errors.rb', line 359
def (attribute) attribute = attribute.to_sym [attribute].map { || (attribute, ) } 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 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 optionshash (in theactivemodel.errorsscope)
- 
activemodel.errors.messages.blank
- 
errors.attributes.title.blank
- 
errors.messages.blank
# File 'activemodel/lib/active_model/errors.rb', line 401
def (attribute, type = :invalid, = {}) type = .delete(:) if [:].is_a?(Symbol) if @base.class.respond_to?(:i18n_scope) i18n_scope = @base.class.i18n_scope.to_s defaults = @base.class.lookup_ancestors.flat_map do |klass| [ :"#{i18n_scope}.errors.models.#{klass.model_name.i18n_key}.attributes.#{attribute}.#{type}", :"#{i18n_scope}.errors.models.#{klass.model_name.i18n_key}.#{type}" ] end defaults << :"#{i18n_scope}.errors.messages.#{type}" else defaults = [] end defaults << :"errors.attributes.#{attribute}.#{type}" defaults << :"errors.messages.#{type}" key = defaults.shift defaults = .delete(:) if [:] value = (attribute != :base ? @base.send(:read_attribute_for_validation, attribute) : nil) = { default: defaults, model: @base.model_name.human, attribute: @base.class.human_attribute_name(attribute), value: value, object: @base }.merge!() I18n.translate(key, ) end
#has_key?(attribute)
Alias for #include?.
# File 'activemodel/lib/active_model/errors.rb', line 130
alias :has_key? :include?
    #include?(attribute)  ⇒ Boolean 
    Also known as: #has_key?, #key?
  
Returns true if the error messages include an error for the given key attribute, false otherwise.
person.errors.        # => {:name=>["cannot be nil"]}
person.errors.include?(:name) # => true
person.errors.include?(:age)  # => false# File 'activemodel/lib/active_model/errors.rb', line 126
def include?(attribute) attribute = attribute.to_sym .key?(attribute) && [attribute].present? end
#key?(attribute)
Alias for #include?.
# File 'activemodel/lib/active_model/errors.rb', line 131
alias :key? :include?
#keys
Returns all message keys.
person.errors. # => {:name=>["cannot be nil", "must be specified"]}
person.errors.keys     # => [:name]# File 'activemodel/lib/active_model/errors.rb', line 198
def keys .select do |key, value| !value.empty? end.keys end
#merge!(other)
Merges the errors from other.
other - The Errors instance.
Examples
person.errors.merge!(other)# File 'activemodel/lib/active_model/errors.rb', line 105
def merge!(other) @messages.merge!(other.) { |_, ary1, ary2| ary1 + ary2 } @details.merge!(other.details) { |_, ary1, ary2| ary1 + ary2 } end
#size Also known as: #count
# File 'activemodel/lib/active_model/errors.rb', line 179
def size values.flatten.size end
#to_a
Alias for #full_messages.
# File 'activemodel/lib/active_model/errors.rb', line 347
alias :to_a :
#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 244
def to_hash( = false) if .each_with_object({}) do |(attribute, array), | [attribute] = array.map { || (attribute, ) } end else without_default_proc() end end
#to_xml(options = {})
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>#values
Returns all message values.
person.errors. # => {:name=>["cannot be nil", "must be specified"]}
person.errors.values   # => [["cannot be nil", "must be specified"]]# File 'activemodel/lib/active_model/errors.rb', line 188
def values .select do |key, value| !value.empty? end.values end