So I've got two records from Model, a and b. I want to do this:
def do_codependant_stuff(a,b)
a.attribute += b.attribute2
b.attribute = b.stuff+a.stuff
end
I keep hearing fat model, skinny controller, and no business logic in views, so I've put this in my Model model. Based on what a user clicks in one of my views, I want to call do_codependant_stuff(a, b) or do_codependant_stuff(b,a).
I've been just using the basic crud controller actions up to this point, and I'm not quite sure how to make this happen. Do I add this logic to my ModelController update action? Because it's technically updating them, just in a more specific way. Or make another action in the controller? How do I call it/set it up? Most of the default new, update etc are somehow called behind the scenes based on their respective views.
And is updating two things at a time bad practice? Should I split the do_codependant_stuff method into two instance methods and call them on each record with the other as a parameter?
Thanks for reading.
Edit: Alright, real world code. I'm displaying on the home page of my app two pictures. The user selects the one they like most. The ratings of these pictures change based on a chess ranking algorithm. This is the relevant section of my picture class.
class Picture < ActiveRecord::Base
...
...
def expected_first_beats_second(picture first, picture second)
1/(1+10**((second.rating-first.rating)/400))
end
def first_beat_second(picA,picB)
Ea = expected_first_beats_second(picA,picB)
picA.rating += 50*(1-Ea)
picB.rating += 50*(-(1-Ea))
end
end
The partial I'm using for the view just displays two pictures at random so far with
<% picA = Picture.offset(rand(Picture.count)).first %>
<% picB = Picture.offset(rand(Picture.count)).first %>
<div class = "row">
<div class = "col-md-5">
<%= image_tag picA.url, :class => "thumbnail" %>
</div>
<div class = "col-md-5">
<%= image_tag picB.url, :class => "thumbnail" %>
</div>
</div>
I need to somehow link the onclick of those images to the method in the model.
Here's some code to get you started. Note the comments, they're ruby and rails best practices
Controller:
class PC < AC
...
def compare
# count query once, save the number
count = Picture.count
@pic_a = Picture.offset(rand(count)).first
@pic_b = Picture.offset(rand(count)).first
end
def compare_submit
# Note variables are snake cased, not camel cased
pic_a = Picture.find(params[:winner_id])
pic_b = Picture.find(params[:loser_id])
pic_a.beats(pic_b)
redirect to compare_pictures_path # Or wherever
end
...
end
Any sort of querying should be done in the controller or model. You essentially should never directly access a model in your view. At this point your view has access to the instance variables set in the controller: @pic_a
and @pic_b
View:
<%= link_to compare_submit_pictures_path(winner_id: @pic_a.id, loser_id: @pic_b.id) do %>
<%= image_tag @pic_a.url, :class => "thumbnail" %>
<% end %>
<%= link_to compare_submit_pictures_path(winner_id: @pic_b.id, loser_id: @pic_a.id) do %>
<%= image_tag @pic_b.url, :class => "thumbnail" %>
<% end %>
So we just linked to a new path (see routes below) that will pass two parameters: winner_id
and loser_id
so whichever picture the user clicks on you'll know which one they chose and which one they didn't choose.
Model:
class Picture < AR::Base
# Method arguments don't need a type declaration
def beats(loser)
# Always lowercase variables
ea = 1/(1+10**((loser.rating-self.rating)/400))
self.rating += 50*(1-ea)
loser.rating += 50*(-(1-ea))
self.save
loser.save
end
end
This explicitly uses self
for clarity, which isn't necessary. Calling save
or rating = ...
implicitly calls it on self since we're in the context of an instance method on the picture Model.
Routes:
resource :pictures do
collection do
get :compare
get :compare_submit
end
end
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