Active Record Attribute Methods
- MODULE ActiveRecord::AttributeMethods::BeforeTypeCast
- MODULE ActiveRecord::AttributeMethods::ClassMethods
- MODULE ActiveRecord::AttributeMethods::Dirty
- MODULE ActiveRecord::AttributeMethods::PrimaryKey
- MODULE ActiveRecord::AttributeMethods::Query
- MODULE ActiveRecord::AttributeMethods::Read
- MODULE ActiveRecord::AttributeMethods::Serialization
- MODULE ActiveRecord::AttributeMethods::TimeZoneConversion
- MODULE ActiveRecord::AttributeMethods::Write
- #
- A
- H
- R
- ActiveModel::AttributeMethods
- ActiveRecord::AttributeMethods::Read
- ActiveRecord::AttributeMethods::Write
- ActiveRecord::AttributeMethods::BeforeTypeCast
- ActiveRecord::AttributeMethods::Query
- ActiveRecord::AttributeMethods::PrimaryKey
- ActiveRecord::AttributeMethods::TimeZoneConversion
- ActiveRecord::AttributeMethods::Dirty
- ActiveRecord::AttributeMethods::Serialization
Constants
RESTRICTED_CLASS_METHODS | = | %w(private public protected allocate new name superclass) |
Instance Public methods
[](attr_name) Link
Returns the value of the attribute identified by attr_name
after it has been type cast. (For information about specific type casting behavior, see the types under ActiveModel::Type
.)
class Person < ActiveRecord::Base
belongs_to :organization
end
person = Person.new(name: "Francesco", date_of_birth: "2004-12-12")
person[:name] # => "Francesco"
person[:date_of_birth] # => Date.new(2004, 12, 12)
person[:organization_id] # => nil
Raises ActiveModel::MissingAttributeError
if the attribute is missing. Note, however, that the id
attribute will never be considered missing.
person = Person.select(:name).first
person[:name] # => "Francesco"
person[:date_of_birth] # => ActiveModel::MissingAttributeError: missing attribute 'date_of_birth' for Person
person[:organization_id] # => ActiveModel::MissingAttributeError: missing attribute 'organization_id' for Person
person[:id] # => nil
[]=(attr_name, value) Link
Updates the attribute identified by attr_name
using the specified value
. The attribute value will be type cast upon being read.
class Person < ActiveRecord::Base
end
person = Person.new
person[:date_of_birth] = "2004-12-12"
person[:date_of_birth] # => Date.new(2004, 12, 12)
accessed_fields() Link
Returns the name of all database fields which have been read from this model. This can be useful in development mode to determine which fields need to be selected. For performance critical pages, selecting only the required fields can be an easy performance win (assuming you aren’t using all of the fields on the model).
For example:
class PostsController < ActionController::Base
after_action :print_accessed_fields, only: :index
def index
@posts = Post.all
end
private
def print_accessed_fields
p @posts.first.accessed_fields
end
end
Which allows you to quickly change your code to:
class PostsController < ActionController::Base
def index
@posts = Post.select(:id, :title, :author_id, :updated_at)
end
end
attribute_for_inspect(attr_name) Link
Returns an #inspect
-like string for the value of the attribute attr_name
. String
attributes are truncated up to 50 characters. 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 00:15:07.000000000 +0000\""
person.attribute_for_inspect(:tag_ids)
# => "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]"
attribute_names() Link
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"]
attribute_present?(attr_name) Link
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 activerecord/lib/active_record/attribute_methods.rb, line 386 def attribute_present?(attr_name) attr_name = attr_name.to_s attr_name = self.class.attribute_aliases[attr_name] || attr_name value = _read_attribute(attr_name) !value.nil? && !(value.respond_to?(:empty?) && value.empty?) end
attributes() Link
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}
has_attribute?(attr_name) Link
Returns true
if the given attribute is in the attributes hash, otherwise false
.
class Person < ActiveRecord::Base
alias_attribute :new_name, :name
end
person = Person.new
person.has_attribute?(:name) # => true
person.has_attribute?(:new_name) # => true
person.has_attribute?('age') # => true
person.has_attribute?(:nothing) # => false
respond_to?(name, include_private = false) Link
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 defines 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 activerecord/lib/active_record/attribute_methods.rb, line 290 def respond_to?(name, include_private = false) return false unless super # If the result is true then check for the select case. # For queries selecting a subset of columns, return false for unselected columns. if @attributes if name = self.class.symbol_column_to_string(name.to_sym) return _has_attribute?(name) end end true end