LazyLoadAttributes
Simple "Ruby core"-inspired syntactic sugar for defining cached, lazy-loaded attributes which intuitively handle inheritence and attribute redefinition.
Installation
Add this line to your application's Gemfile:
gem 'lazy_load_attributes'
And then execute:
$ bundle install
Or install it yourself as:
$ gem install lazy_load_attributes
Usage
The class-level lazy_attr_reader
method defines a lazy-loaded attribute.
The class-level lazy_attr_accessor
method additionally defines a setter for the lazy-loaded attribute.
The instance-level eager_load_attributes!
method eager loads all lazy-loaded attributes which haven't been loaded.
A simple use-case:
require "lazy_load_attributes"
class Example
extend LazyLoadAttributes
lazy_attr_reader(:lazy_attr) { puts "loaded"; lazy_attr_method }
def lazy_attr_method
"lazy value"
end
end
example = Example.new
example.lazy_attr
# loaded
# => "lazy value"
example.lazy_attr
# => "lazy value"
This illustrates four major powers of LazyLoadAttributes:
- the attribute calls evaluate and return their definition's initializer
- the initializer is not evaluated until the first attribute call
- the initializer is evaluated in the context of the calling instance (i.e.
example
in the sample above), so its instance methods are available during evaluation as they would be within the body of a normal instance method - the initializer is evaluated only once; subsequent attribute calls are served from a cache
Inheritence is handled transparently:
class Superclass
extend LazyLoadAttributes
lazy_attr_reader(:super_attr) { super_attr_value }
lazy_attr_reader(:redefine_attr) { "redefine_attr from Superclass" }
def super_attr_value
"Superclass#super_attr_value"
end
def sub_attr_value
"Superclass#sub_attr_value"
end
end
class Subclass < Superclass
lazy_attr_reader(:redefine_attr) { "redefine_attr from Subclass" }
lazy_attr_reader(:sub_attr) { sub_attr_value }
def super_attr_value
"Subclass#super_attr_value"
end
end
super_instance = Superclass.new
super_instance.super_attr
# => "Superclass#super_attr_value"
super_instance.redefine_attr
# => "redefine_attr from Superclass"
sub_instance = Subclass.new
sub_instance.super_attr
# => "Subclass#super_attr_value"
sub_instance.sub_attr
# => "Superclass#sub_attr_value"
sub_instance.redefine_attr
# => "redefine_attr from Subclass"
The call to sub_instance.super_attr
shows that the instance methods used by an initializer respect inheritence even when the attribute itself is defined in the superclass
The call to sub_instance.sub_attr
shows that initializers used by definitions in a subclass have access to instance methods defined in a superclass
The call to sub_instance.redefine_attr
shows that an attribute redefined in a subclass will override its definition in the superclass
Development
After checking out the repo, run bin/setup
to install dependencies. Then, run rake spec
to run the tests. You can also run bin/console
for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install
. To release a new version, update the version number in version.rb
, and then run bundle exec rake release
, which will create a git tag for the version, push git commits and the created tag, and push the .gem
file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/eizengan/lazy_load_attributes. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.
License
The gem is available as open source under the terms of the MIT License.
Code of Conduct
Everyone interacting in the LazyLoadAttributes project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.