Active Record Attribute Methods
- MODULE ActiveRecord::AttributeMethods::BeforeTypeCast
- MODULE ActiveRecord::AttributeMethods::ClassMethods
- 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
- C
- H
- R
- ActiveModel::AttributeMethods
- ActiveRecord::AttributeMethods::Read
- ActiveRecord::AttributeMethods::Write
- ActiveRecord::AttributeMethods::BeforeTypeCast
- ActiveRecord::AttributeMethods::Query
- ActiveRecord::AttributeMethods::PrimaryKey
- ActiveRecord::AttributeMethods::TimeZoneConversion
- ActiveRecord::AttributeMethods::Serialization
Returns the value of the attribute identified by attr_name
after it has been typecast (for example, “2004-12-12” in a data 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
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
Returns an #inspect
-like string for the value of the attribute
attr_name
. String attributes are
truncated upto 50 characters, and Date and Time attributes are returned in the
:db
format. 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 D...\"" person.attribute_for_inspect(:created_at) # => "\"2012-10-22 00:15:07\""
# File activerecord/lib/active_record/attribute_methods.rb, line 260 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)}") 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"]
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
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}
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
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
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 activerecord/lib/active_record/attribute_methods.rb, line 189 def respond_to?(name, include_private = false) name = name.to_s self.class.define_attribute_methods unless self.class.attribute_methods_generated? 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.present? && self.class.column_names.include?(name) return has_attribute?(name) end return true end