module ActiveRecord::AttributeMethods

Active Record Attribute Methods

Constants

AttrNames
BLACKLISTED_CLASS_METHODS

Public Instance Methods

[](attr_name) click to toggle source

Returns the value of the attribute identified by attr_name after it has been typecast (for example, “2004-12-12” in a date column is cast to a date object, like Date.new(2004, 12, 12)). It raises ActiveModel::MissingAttributeError if the identified attribute is missing.

Alias for the read_attribute method.

class Person < ActiveRecord::Base
  belongs_to :organization
end

person = Person.new(name: 'Francesco', age: '22')
person[:name] # => "Francesco"
person[:age]  # => 22

person = Person.select('id').first
person[:name]            # => ActiveModel::MissingAttributeError: missing attribute: name
person[:organization_id] # => ActiveModel::MissingAttributeError: missing attribute: organization_id
# File lib/active_record/attribute_methods.rb, line 377
def [](attr_name)
  read_attribute(attr_name) { |n| missing_attribute(n, caller) }
end
[]=(attr_name, value) click to toggle source

Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).

class Person < ActiveRecord::Base
end

person = Person.new
person[:age] = '22'
person[:age] # => 22
person[:age] # => Fixnum
# File lib/active_record/attribute_methods.rb, line 391
def []=(attr_name, value)
  write_attribute(attr_name, value)
end
attribute_for_inspect(attr_name) click to toggle source

Returns an #inspect-like string for the value of the attribute attr_name. String attributes are truncated upto 50 characters, Date and Time attributes are returned in the :db format, Array attributes are truncated upto 10 values. Other attributes return the value of #inspect without modification.

person = Person.create!(name: 'David Heinemeier Hansson ' * 3)

person.attribute_for_inspect(:name)
# => "\"David Heinemeier Hansson David Heinemeier Hansson ...\""

person.attribute_for_inspect(:created_at)
# => "\"2012-10-22 00:15:07\""

person.attribute_for_inspect(:tag_ids)
# => "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...]"
# File lib/active_record/attribute_methods.rb, line 308
def attribute_for_inspect(attr_name)
  value = read_attribute(attr_name)

  if value.is_a?(String) && value.length > 50
    "#{value[0, 50]}...".inspect
  elsif value.is_a?(Date) || value.is_a?(Time)
    %Q("#{value.to_s(:db)}")
  elsif value.is_a?(Array) && value.size > 10
    inspected = value.first(10).inspect
    %Q(#{inspected[0...-1]}, ...])
  else
    value.inspect
  end
end
attribute_names() click to toggle source

Returns an array of names for the attributes available on this object.

class Person < ActiveRecord::Base
end

person = Person.new
person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]
# File lib/active_record/attribute_methods.rb, line 268
def attribute_names
  @attributes.keys
end
attribute_present?(attribute) click to toggle source

Returns true if the specified attribute has been set by the user or by a database load and is neither nil nor empty? (the latter only applies to objects that respond to empty?, most notably Strings). Otherwise, false. Note that it always returns true with boolean attributes.

class Task < ActiveRecord::Base
end

person = Task.new(title: '', is_done: false)
person.attribute_present?(:title)   # => false
person.attribute_present?(:is_done) # => true
person.name = 'Francesco'
person.is_done = true
person.attribute_present?(:title)   # => true
person.attribute_present?(:is_done) # => true
# File lib/active_record/attribute_methods.rb, line 338
def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
end
attributes() click to toggle source

Returns a hash of all the attributes with their names as keys and the values of the attributes as values.

class Person < ActiveRecord::Base
end

person = Person.create(name: 'Francesco', age: 22)
person.attributes
# => {"id"=>3, "created_at"=>Sun, 21 Oct 2012 04:53:04, "updated_at"=>Sun, 21 Oct 2012 04:53:04, "name"=>"Francesco", "age"=>22}
# File lib/active_record/attribute_methods.rb, line 280
def attributes
  attribute_names.each_with_object({}) { |name, attrs|
    attrs[name] = read_attribute(name)
  }
end
column_for_attribute(name) click to toggle source

Returns the column object for the named attribute. Returns nil if the named attribute not exists.

class Person < ActiveRecord::Base
end

person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

person.column_for_attribute(:nothing)
# => nil
# File lib/active_record/attribute_methods.rb, line 355
def column_for_attribute(name)
  # FIXME: should this return a null object for columns that don't exist?
  self.class.columns_hash[name.to_s]
end
has_attribute?(attr_name) click to toggle source

Returns true if the given attribute is in the attributes hash, otherwise false.

class Person < ActiveRecord::Base
end

person = Person.new
person.has_attribute?(:name)    # => true
person.has_attribute?('age')    # => true
person.has_attribute?(:nothing) # => false
# File lib/active_record/attribute_methods.rb, line 256
def has_attribute?(attr_name)
  @attributes.has_key?(attr_name.to_s)
end
respond_to?(name, include_private = false) click to toggle source

A Person object with a name attribute can ask person.respond_to?(:name), person.respond_to?(:name=), and person.respond_to?(:name?) which will all return true. It also define the attribute methods if they have not been generated.

class Person < ActiveRecord::Base
end

person = Person.new
person.respond_to(:name)    # => true
person.respond_to(:name=)   # => true
person.respond_to(:name?)   # => true
person.respond_to('age')    # => true
person.respond_to('age=')   # => true
person.respond_to('age?')   # => true
person.respond_to(:nothing) # => false
Calls superclass method
# File lib/active_record/attribute_methods.rb, line 228
def respond_to?(name, include_private = false)
  name = name.to_s
  self.class.define_attribute_methods
  result = super

  # If the result is false the answer is false.
  return false unless result

  # If the result is true then check for the select case.
  # For queries selecting a subset of columns, return false for unselected columns.
  # We check defined?(@attributes) not to issue warnings if called on objects that
  # have been allocated but not yet initialized.
  if defined?(@attributes) && @attributes.any? && self.class.column_names.include?(name)
    return has_attribute?(name)
  end

  return true
end

Private Instance Methods

arel_attributes_with_values(attribute_names) click to toggle source

Returns a Hash of the Arel::Attributes and attribute values that have been typecasted for use in an Arel insert/update method.

# File lib/active_record/attribute_methods.rb, line 428
def arel_attributes_with_values(attribute_names)
  attrs = {}
  arel_table = self.class.arel_table

  attribute_names.each do |name|
    attrs[arel_table[name]] = typecasted_attribute_value(name)
  end
  attrs
end
attributes_for_create(attribute_names) click to toggle source

Filters out the primary keys, from the attribute names, when the primary key is to be generated (e.g. the id attribute has no value).

# File lib/active_record/attribute_methods.rb, line 447
def attributes_for_create(attribute_names)
  attribute_names.select do |name|
    column_for_attribute(name) && !(pk_attribute?(name) && id.nil?)
  end
end
attributes_for_update(attribute_names) click to toggle source

Filters the primary keys and readonly attributes from the attribute names.

# File lib/active_record/attribute_methods.rb, line 439
def attributes_for_update(attribute_names)
  attribute_names.select do |name|
    column_for_attribute(name) && !readonly_attribute?(name)
  end
end
pk_attribute?(name) click to toggle source
# File lib/active_record/attribute_methods.rb, line 457
def pk_attribute?(name)
  column_for_attribute(name).primary
end
readonly_attribute?(name) click to toggle source
# File lib/active_record/attribute_methods.rb, line 453
def readonly_attribute?(name)
  self.class.readonly_attributes.include?(name)
end
typecasted_attribute_value(name) click to toggle source
# File lib/active_record/attribute_methods.rb, line 461
def typecasted_attribute_value(name)
  # FIXME: we need @attributes to be used consistently.
  # If the values stored in @attributes were already typecasted, this code
  # could be simplified
  read_attribute(name)
end