A quick run down on the presenter pattern in rails, code for the talk is here https://github.com/ridget/presenters_app

1. PRESENTERS
with a guest appearance from decorators

2. HI
• tomridge2@gmail.com
• @tjridge
• github.com/ridget

3. LETS BUILD AN APP

4. VIEW RELATED LOGIC
• welp

5. LETS PUT IT IN A HELPER!

7. HELPERS AREN’T AWESOME
• at least for this task
• they share a global namespace
• aren’t a very oo way of solving the problem
• great for shared logic that doesn't relate to the
object. Use sparingly

8. I KNOW MODELS!
• also nope
• All these if conditions relate to the display of data
• Don’t overload your model with that level of
responsibility

9. ENTER PRESENTERS
• Presenters are a simple class with knowledge of
the model and the view.
• Not a stretch to call them a ViewModel

10. PURPOSE
• Presenters help to achieve adherence to SRP
• A Presenter’s purpose is a decorator who has the
job of massaging the decorated object into a ui/
view friendly manner.

11. DECORATOR?
• Taking one object and adding, replacing or
extending its behaviour, whilst allowing access to
the underlying objects methods.

12. PRESENTERS VS DECORATORS
• A decorator isn’t always a presenter, but a
presenter is always likely to be a decorator.

13. END RESULT
• This is more in line with a decorator approach
• We just delegate to the underlying object

14. MULTIPLE OBJECTS?
• ensure you delegate methods to the underlying
objects

15. MULTIPLE RECORDS?
• Just create a wrap method to instantiate your
presenter/decorator across multiple records.

16. OTHER OPTIONS?
• Draper
• Great for when things start getting more
complex

17. OTHER VALUE POINTS
• Easy-ish to test
• less conditionals in your views
• happier designers/front end developers

18. CONS
• More objects == harder to learn the codebase
• Don’t introduce them until you need to.

19. GREAT RESOURCES
• Railscasts - draper and presenters from scratch
(pro)
• http://new-bamboo.co.uk/blog/2013/04/17/rails-presenters-
skinny-everything
• http://robertomurray.co.uk/blog/2014/decorators-presenters-
delegators-rails/

20. QUESTIONS?