The document discusses problems with using instance variables (@ivars) in controllers and proposes a solution called "decent_exposure". It notes that @ivars in controllers lead to duplication across actions and unclear variable scope. Decent_exposure avoids this by allowing controllers to expose variables through blocks, making their values and initialization explicit and avoiding duplication. An example controller uses decent_exposure to expose collections and objects without @ivars, improving clarity and maintainability.

1. decent_exposure
Controladores sin @ivars
Leo Soto M.

2. Controladores sin @ivars

3. Controladores sin @ivars
¿Por qué?

4. @ivars == estado dentro de una clase

5. @ivars en controladores == HACK

7. Problemas prácticos de los controladores

8. 1. Duplicación

9. class PostsController
def index
@posts = Post.all
end
def create
@post = Post.new(params[:post])
@post.save
end
def new
@post = Post.new
end

10. def show
@post = Post.find(params[:id])
end
def edit
@post = Post.find(params[:id])
end
def update
@post = Post.find(params[:id])
@post.update_attributes(params[:post])
end
def destroy
@post = Post.find(params[:id])
@post.destroy
end
end

11. def show
@post = Post.find(params[:id])
end
def edit
@post = Post.find(params[:id])
end
def update
@post = Post.find(params[:id])
@post.update_attributes(params[:post])
end
def destroy
@post = Post.find(params[:id])
@post.destroy
end
end

12. 2. ¿Qué variables puedo usar?

13. controlador.rb
def foo
@x = ...
@y = ...
@z = ...
end
def bar
@z = ...
end
def baz
@x = ...
@z = ...
end

14. foo.html.erb
...
<% render :partial => “some_partial” %>
...

15. baz.html.erb
...
<% render :partial => “some_partial” %>
...

16. _some_partial.html.erb
...
<div id=“BOOM”>
<%= @y.to_s %>
</div>
...

17. ¿Soluciones?

18. controlador.rb
before_filter :load_y
def load_y; @y = ... ; end
def foo
@x = ...
@z = ...
end
def bar
@z = ...
end
def baz
@x = ...
@z = ...
end

19. controlador.rb
helper_method :y
def y; @y ||= ... ; end
def foo
@x = ...
@z = ...
end
def bar
@z = ...
end
def baz
@x = ...
@z = ...
end

20. Introduciendo decent_exposure

21. controlador.rb
expose(:y) { ... }
def foo
@x = ...
@z = ...
end
def bar
@z = ...
end
def baz
@x = ...
@z = ...
end

22. controlador.rb
expose(:y) { ... }
expose(:x) { ... }
expose(:z) { ... }

23. Un ejemplo real

24. class Admin::PromotionsController < AdminController
expose(:promotions) { Promotion.all }
expose(:promotion) do
params[:id] ? Promotion.find(params[:id]) :
Promotion.new(params[:promotion])
end
def create
if promotion.save
redirect_to :action => :index
else
render :new
end
end
end

25. class Admin::PromotionsController < AdminController
expose(:promotions) { Promotion.all }
expose(:promotion)
def create
if promotion.save
redirect_to :action => :index
else
render :new
end
end
end

26. https://github.com/voxdolo/decent_exposure