Decorator & Presenter Design Pattern

Let have a short look at the Decorator & Presenter Design Pattern with the Draper Gem.

Transcript

1. DECORATOR & PRESENTER
   DESIGN PATTERN
   @DonSchado | 21.05.2014
   

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2. WHY?
   

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3. Because your controllers become bloated
   
   and logic begins to creep into your views (templates)
   

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4. implement procedural helpers or adding view related bulk to your models?
   Solutions?
   

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5. implement procedural helpers or adding view related bulk to your models?
   Solutions?
   helpers are shit making fat models even fatter?

   No class should be fat. Ever.
   

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6. Why are helpers shit?
   http://nicksda.apotomo.de/2011/10/rails-misapprehensions-helpers-are-shit/
   „all helpers are mixed into the view
   automatically (…) [and are] globally available“
   „There is nothing wrong with having those little
   helpers in your view. What I don’t like is that
   they are called without an obvious receiver –
   they look and feel like functions. This is wrong.“
   

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7. Why are helpers shit?
   http://blog.steveklabnik.com/posts/2011-09-09-better-ruby-presenters
   „No seriously, helpers suck“
   „Why is it in Ruby that everything is an
   object, even integers, yet as soon as we
   need to format a date, we all turn into
   Dijkstra and bust out structured
   programming?“
   

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8. DECORATOR
   

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9. Decorator pattern (also known as wrapper) is a design pattern that
   allows to dynamically add behavior to an individual object.
   can be used on it’s own
   
   or wrapped by decorator
   each decorator HAS_A (wraps)
   
   a component (holds a reference)
   (composition)
   (inheritance)
   

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10. The decorator wraps the model, and deals only with presentational concerns.
    
    In the controller, you decorate the article before handing it off to the view
    

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11. https://github.com/drapergem/draper
    Draper: View Models for Rails
    Draper adds an object-oriented layer of
    presentation logic to your Rails application
    

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15. PRESENTER
    

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16. A presenter is a special case of the "Decorator design pattern".
    http://sokolmichael.com/posts/2012-01-14-model-view-controller-presenter-better-separation-of-concern
    MVCP - Better Separation of Concern
    

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17. http://blog.jayfields.com/2007/03/rails-presenter-pattern.html
    Presenter was inspired by the various GUI
    patterns documented by Martin Fowler.
    An architecture that uses the Presenter
    pattern provides view specific data as
    attributes of an instance of the
    Presenter. The Presenter's state is an
    aggregation of model and user entered data.
    

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20. 7 Patterns to Refactor Fat ActiveRecord Models
    http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
    Service Objects
    Value Objects
    Form Objects
    Query Objects
    View Objects
    Policy Objects
    Decorators
    further reading:
    

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21. thx!(and have fun refactoring all the fat classes)
    

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