Refactoring of many if statements for params[...], inside controller action - ruby-on-rails

Question

I have such code, for making chain selects in my form
View for index action:
<%= form_tag do %>
<%= collection_select(*#brands_select_params) %>
<%= collection_select(*#car_models_select_params) %>
<%= collection_select(*#production_years_select_params) %>
<% # Пока еще никто ничего не выбрал %>
<%= submit_tag "Send", :id => "submit", :name => "submit" %>
And my controller:
class SearchController < ApplicationController
def index
#brands = Brand.all
#car_models = CarModel.all
if (params[:brand].blank?)
#brands_select_params = [:brand, :id, #brands, :id, :name, :prompt => "Выбирай брэнд"]
if params[:car_model].blank?
#car_models_select_params = [:car_model, :id, #car_models, :id, :name, { :prompt => "Model" }, \
{ :disabled => "disabled" }]
#production_years_select_params = [:production_year, :id, #car_models, :id, :name, { :prompt => "Year" }, \
{ :disabled => "disabled" }]
end
else
#brands_select_params = [:brand, :id, #brands, :id, :name, { :selected => params[:brand][:id] } ]
if params[:car_model].blank?
#car_models_select_params = [:car_model, :id, Brand.find(params[:brand][:id]).car_models, :id, :name, \
{ :prompt => "And model now" } ]
#production_years_select_params = [:production_year, :id, #car_models, :id, :name, { :prompt => "Year" }, \
{ :disabled => "disabled" } ]
else
#car_models_select_params = [:car_model, :id, Brand.find(params[:brand][:id]).car_models, :id, :name, \
{ :selected => params[:car_model][:id] } ] unless params[:car_model][:id].empty?
#production_years_select_params = [:production_year, :id, CarModel.find(params[:car_model][:id]).production_years, :id, :year, \
{ :prompt => "And year now" } ] unless params[:car_model][:id].empty?
end
end
end
end
As you can see, too many ifs in my controller code. And i gonna add more conditions there. After that anyone who read that code will get brain corruption. So i just wanna make it in real Ruby way, but don't know how. Please, help, guys. How should i refactor this bunch of crap?

Answer 1

I think a big part of the problem is you're doing too much in your controller. Generating markup (and IMO that includes building parameter lists for form helpers) should be done in views and view helpers. So:
module SearchHelper
def brand_select brands, options={}
collection_select :brand, :id, brands, :id, :name, :options
end
def car_model_select car_models, options={}
collection_select :car_model, :id, car_models, :id, :name, options
end
def production_year_select years, options={}
collection_select :production_year, :id, years, :id, :year, options
end
end
Then you can cut your controller down to this:
def index
#brands = Brand.all
#car_models = CarModel.all
#selected_brand_id = params[:brand] && params[:brand][:id]
#selected_car_model_id = params[:car_model] && params[:car_model][:id]
#production_years = #selected_car_model_id ?
[] : CarModel.find(#selected_car_model_id).production_years
end
And in your view:
<%= brand_select #brands, :prompt => "Выбирай брэнд",
:selected => #selected_brand_id
%>
<%= car_model_select #car_models, :prompt => "Model",
:selected => #selected_car_model_id
%>
<%= production_year_select #production_years, :prompt => "Year",
:selected => #selected_car_id
%>
I suspect you could simplify this even more using form_for and fields_for and get rid of the helpers entirely, but it depends a bit on how your model associations are set up.

Answer 2

There is no obvious solution to this kind of problem.
Generally, I try to keep the if / else architecture very clear and export all code into separate methods. 2 advantages here:
readability
easier unit testing
For your case, it would be:
class SearchController < ApplicationController
def index
#brands = Brand.all
#car_models = CarModel.all
if (params[:brand].blank?)
#brands_select_params = [:brand, :id, #brands, :id, :name, :prompt => "Выбирай брэнд"]
if params[:car_model].blank?
#car_models_select_params, #production_years_select_params = get_card_model(#car_models)
end
else
#brands_select_params = [:brand, :id, #brands, :id, :name, { :selected => params[:brand][:id] } ]
if params[:car_model].blank?
#car_models_select_params, #production_years_select_params = foo_method(#car_models)
else
#car_models_select_params, #production_years_select_params = bar_method
end
end
end
def get_card_model car_models
[
[:car_model, :id, car_models, :id, :name, { :prompt => "Model" }, { :disabled => "disabled" }],
[:production_year, :id, car_models, :id, :name, { :prompt => "Year" }, { :disabled => "disabled" }]
]
end
end