ruby-on-rails - 重构 params[...] 的许多 if 语句，在 Controller 操作中

Question

我有这样的代码，用于在我的表单中进行链式选择查看索引操作:

<%= 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" %>

还有我的 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

如您所见，我的 Controller 代码中有太多 if。我要在那里添加更多条件。之后，任何阅读该代码的人都会脑部腐败。所以我只想以真正的 Ruby 方式实现它，但不知道如何实现。请帮忙，伙计们。我应该如何重构这些废话？

Answer 1

我认为问题的很大一部分是您在 Controller 中做的太多了。生成标记(以及包括为表单助手构建参数列表的 IMO)应该在 View 和 View 助手中完成。所以:

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

然后你可以把你的 Controller 缩减成这样:

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

在你看来:

<%= 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
%>

我怀疑您可以使用 form_for and fields_for 进一步简化它并完全摆脱助手，但这在一定程度上取决于您的模型关联的设置方式。