module ActiveRecord::AttributeMethods
Active Record Attribute Methods¶ ↑
Constants
- AttrNames
- BLACKLISTED_CLASS_METHODS
Public Instance Methods
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.
Note: :id
is always present.
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 358 def [](attr_name) read_attribute(attr_name) { |n| missing_attribute(n, caller) } end
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 372 def []=(attr_name, value) write_attribute(attr_name, value) end
Returns an #inspect
-like string for the value of the attribute
attr_name
. String attributes are truncated up to 50
characters, Date and Time attributes are returned in the :db
format, Array attributes are truncated up to 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 304 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
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 271 def attribute_names @attributes.keys end
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 task = Task.new(title: '', is_done: false) task.attribute_present?(:title) # => false task.attribute_present?(:is_done) # => true task.title = 'Buy milk' task.is_done = true task.attribute_present?(:title) # => true task.attribute_present?(:is_done) # => true
# File lib/active_record/attribute_methods.rb, line 334 def attribute_present?(attribute) value = _read_attribute(attribute) !value.nil? && !(value.respond_to?(:empty?) && value.empty?) end
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 283 def attributes @attributes.to_hash end
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 259 def has_attribute?(attr_name) @attributes.key?(attr_name.to_s) end
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
# File lib/active_record/attribute_methods.rb, line 235 def respond_to?(name, include_private = false) return false unless super name = name.to_s # 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) && self.class.column_names.include?(name) return has_attribute?(name) end return true end
Private Instance Methods
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 402 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
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 421 def attributes_for_create(attribute_names) attribute_names.reject do |name| pk_attribute?(name) && id.nil? end end
Filters the primary keys and readonly attributes from the attribute names.
# File lib/active_record/attribute_methods.rb, line 413 def attributes_for_update(attribute_names) attribute_names.reject do |name| readonly_attribute?(name) end end
# File lib/active_record/attribute_methods.rb, line 431 def pk_attribute?(name) name == self.class.primary_key end
# File lib/active_record/attribute_methods.rb, line 427 def readonly_attribute?(name) self.class.readonly_attributes.include?(name) end
# File lib/active_record/attribute_methods.rb, line 435 def typecasted_attribute_value(name) _read_attribute(name) end