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COLUMN_NAME_ORDER_WHITELIST | = | / \A (?:\w+\.)? \w+ (?:\s+asc|\s+desc)? (?:\s+nulls\s+(?:first|last))? \z /ix |
Regexp whitelist. Matches the following:
|
||
COLUMN_NAME_WHITELIST | = | /\A(?:\w+\.)?\w+\z/i |
Regexp whitelist. Matches the following:
|
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.
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].class # => Integer
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
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. 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, 11]"
# File activerecord/lib/active_record/attribute_methods.rb, line 346 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) %("#{value.to_s(:db)}") else value.inspect end end
Returns true
if attribute
is an attribute method
and table exists, false
otherwise.
class Person < ActiveRecord::Base
end
Person.attribute_method?('name') # => true
Person.attribute_method?(:age=) # => true
Person.attribute_method?(:nothing) # => false
Returns an array of column names as strings if it's not an abstract class and table exists. Otherwise it returns an empty array.
class Person < ActiveRecord::Base
end
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
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
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 a
ActiveRecord::ConnectionAdapters::NullColumn
if the named
attribute does not exist.
class Person < ActiveRecord::Base
end
person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>
person.column_for_attribute(:nothing)
# => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
A class method is 'dangerous' if it is already (re)defined by Active Record, but not by any ancestors. (So 'puts' is not dangerous but 'new' is.)
Returns true if the given attribute exists, otherwise false.
class Person < ActiveRecord::Base
end
Person.has_attribute?('name') # => true
Person.has_attribute?(:age) # => true
Person.has_attribute?(:nothing) # => false
Raises an ActiveRecord::DangerousAttributeError
exception when an Active Record method is defined in the model, otherwise
false
.
class Person < ActiveRecord::Base
def save
'already defined by Active Record'
end
end
Person.instance_method_already_implemented?(:save)
# => ActiveRecord::DangerousAttributeError: save is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name.
Person.instance_method_already_implemented?(:name)
# => false
# File activerecord/lib/active_record/attribute_methods.rb, line 89 def instance_method_already_implemented?(method_name) if dangerous_attribute_method?(method_name) raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name." end if superclass == Base super else # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass # defines its own attribute method, then we don't want to overwrite that. defined = method_defined_within?(method_name, superclass, Base) && ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods) defined || super end 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 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 270 def respond_to?(name, include_private = false) return false unless super case name when :to_partial_path name = "to_partial_path".freeze when :to_model name = "to_model".freeze else name = name.to_s end # 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 true end