Presenter & DecoratorIn Rails
Decorator
What is Decorator in Rails?
A decorator is a design pattern. Its intent, as described in
Design Patterns by the Gang of Four is:
> Attach additional responsibilities to an object
dynamically. Decorators provide a flexible alternative to
subclassing for extending functionality.
Why do we use Decorator?
Refactoring for SRP (Single Responsibility Principle)
Extend behaviors of an object
Try out #1
I have a coffee class which has #cost method.
Class Coffee def cost 2 endend
coffee = Coffee.new()coffee.cost#=> 2
What if I want to add sugar or milk? Assume sugar price is 0.2
and Milk is 0.4
How to implement Decorator?
There is a great post by Dan Croak on how to implement Decorator
in rails.
http://robots.thoughtbot.com/post/14825364877/evaluating-alternative-decorator-implementations-in
When to use Decorator?
When an object knows too much.
When a group of methods describe a possible meaning of
behavior
When want to extend behavior of an object
When fully understand Decorator
Presenter
What is Presenter in Rails?
A form of Decorator
A bridge between the model and view in presentation logic
Why do we use Presenter?
To cleanup views by moving aways all the logic
To keep all presentation logic in one place
How to implement Presenter?
There is a great post by Harold Gimnez on how to implement
Presenter in rails.
http://robots.thoughtbot.com/post/13641910701/tidy-views-and-beyond-with-decorators
Don't confuse with helper with Presenter
Simple logic goes to helper
Logic that don't relate to object, goes to helper
Logic relate to object, goes to Presenter
Too complex logic can also go to Presenter
Q & A
Thanks You
