module ActiveEntity::Attributes::ClassMethods
Public Instance Methods
Defines an attribute with a type on this model. It will override the type of existing attributes if needed. This allows control over how values are converted to and from SQL when assigned to a model. It also changes the behavior of values passed to ActiveEntity::Base.where. This will let you use your domain objects across much of Active Entity, without having to rely on implementation details or monkey patching.
name
The name of the methods to define attribute methods for, and the column which this will persist to.
cast_type
A symbol such as :string
or :integer
, or a type object to be used for this attribute. See the examples below for more information about providing custom type objects.
Options¶ ↑
The following options are accepted:
default
The default value to use when no value is provided. If this option is not passed, the previous default value (if any) will be used. Otherwise, the default will be nil
.
array
(PostgreSQL only) specifies that the type should be an array (see the examples below).
range
(PostgreSQL only) specifies that the type should be a range (see the examples below).
When using a symbol for cast_type
, extra options are forwarded to the constructor of the type object.
Examples¶ ↑
The type detected by Active Entity can be overridden.
# db/schema.rb create_table :store_listings, force: true do |t| t.decimal :price_in_cents end # app/models/store_listing.rb class StoreListing < ActiveEntity::Base end store_listing = StoreListing.new(price_in_cents: '10.1') # before store_listing.price_in_cents # => BigDecimal(10.1) class StoreListing < ActiveEntity::Base attribute :price_in_cents, :integer end # after store_listing.price_in_cents # => 10
A default can also be provided.
# db/schema.rb create_table :store_listings, force: true do |t| t.string :my_string, default: "original default" end StoreListing.new.my_string # => "original default" # app/models/store_listing.rb class StoreListing < ActiveEntity::Base attribute :my_string, :string, default: "new default" end StoreListing.new.my_string # => "new default" class Product < ActiveEntity::Base attribute :my_default_proc, :datetime, default: -> { Time.now } end Product.new.my_default_proc # => 2015-05-30 11:04:48 -0600 sleep 1 Product.new.my_default_proc # => 2015-05-30 11:04:49 -0600
Attributes do not need to be backed by a database column.
# app/models/my_model.rb class MyModel < ActiveEntity::Base attribute :my_string, :string attribute :my_int_array, :integer, array: true attribute :my_float_range, :float, range: true end model = MyModel.new( my_string: "string", my_int_array: ["1", "2", "3"], my_float_range: "[1,3.5]", ) model.attributes # => { my_string: "string", my_int_array: [1, 2, 3], my_float_range: 1.0..3.5 }
Passing options to the type constructor
# app/models/my_model.rb class MyModel < ActiveEntity::Base attribute :small_int, :integer, limit: 2 end MyModel.create(small_int: 65537) # => Error: 65537 is out of range for the limit of two bytes
Creating Custom Types¶ ↑
Users may also define their own custom types, as long as they respond to the methods defined on the value type. The method deserialize
or cast
will be called on your type object, with raw input from the database or from your controllers. See ActiveModel::Type::Value for the expected API. It is recommended that your type objects inherit from an existing type, or from ActiveEntity::Type::Value
class MoneyType < ActiveEntity::Type::Integer def cast(value) if !value.kind_of?(Numeric) && value.include?('$') price_in_dollars = value.gsub(/\$/, '').to_f super(price_in_dollars * 100) else super end end end # config/initializers/types.rb ActiveEntity::Type.register(:money, MoneyType) # app/models/store_listing.rb class StoreListing < ActiveEntity::Base attribute :price_in_cents, :money end store_listing = StoreListing.new(price_in_cents: '$10.00') store_listing.price_in_cents # => 1000
For more details on creating custom types, see the documentation for ActiveModel::Type::Value. For more details on registering your types to be referenced by a symbol, see ActiveEntity::Type.register
. You can also pass a type object directly, in place of a symbol.
Dirty Tracking¶ ↑
The type of an attribute is given the opportunity to change how dirty tracking is performed. The methods changed?
and changed_in_place?
will be called from ActiveModel::Dirty. See the documentation for those methods in ActiveModel::Type::Value for more details.
# File lib/active_entity/attributes.rb, line 170 def attribute(name, cast_type = Type::Value.new, **options) name = name.to_s reload_schema_from_cache self.attributes_to_define_after_schema_loads = attributes_to_define_after_schema_loads.merge( name => [cast_type, options] ) end
This is the low level API which sits beneath attribute
. It only accepts type objects, and will do its work immediately instead of waiting for the schema to load. Automatic schema detection and ClassMethods#attribute
both call this under the hood. While this method is provided so it can be used by plugin authors, application code should probably use ClassMethods#attribute
.
name
The name of the attribute being defined. Expected to be a String
.
cast_type
The type object to use for this attribute.
default
The default value to use when no value is provided. If this option is not passed, the previous default value (if any) will be used. Otherwise, the default will be nil
. A proc can also be passed, and will be called once each time a new value is needed.
cast
or deserialize
.
# File lib/active_entity/attributes.rb, line 197 def define_attribute( name, cast_type, default: NO_DEFAULT_PROVIDED ) attribute_types[name] = cast_type define_default_attribute(name, default, cast_type) end
Private Instance Methods
# File lib/active_entity/attributes.rb, line 222 def define_default_attribute(name, value, type) default_attribute = if value == NO_DEFAULT_PROVIDED _default_attributes[name].with_type(type) else ActiveModel::Attribute::UserProvidedDefault.new( name, value, type, _default_attributes.fetch(name.to_s) { nil }, ) end _default_attributes[name] = default_attribute end