Rails - 如何對層疊集合的結果進行排序選擇表格

Question

我已經將我的級聯collection_select表單按照我想要的方式工作，但現在我想知道如何按字母順序排序子字段的更新結果。在我的控制器

我的自定義操作：

def update_areas 
    city_id = (params[:city_id].nil? || params[:city_id].empty?) ? 0 : params[:city_id].to_i 
    # updates artists and songs based on genre selected 
    if city_id == 0 
    @areas = [] 
    @neighborhoods = [] 

    else 
     city = City.find(params[:city_id]) 
     # map to name and id for use in our options_for_select 
     @areas = city.areas.map{|a| [a.name, a.id]} 
     @neighborhoods = Neighborhood.where(:area_id => city.areas.each{|a| a.id}).map{|s| [s.name, s.id]} 
    end 
    @areas.insert(0, "Select an Area") 
    @neighborhoods.insert(0, "Select a neighborhood") 
end 

def update_neighborhoods 
    # updates songs based on artist selected 
    area = Area.find(params[:area_id]) 
    @neighborhoods = area.neighborhoods.map{|s| [s.name, s.id]}.insert(0, "Select a neighborhood") 
end 

表單代碼：

<div id="city"> 
    <p>City:</p> 
    <%= f.collection_select(:city_id, City.order('name ASC'), :id, :name, {:prompt => "Select a City"}, {:id => 'cities_select'}) %> 
    <br /> 
</div> 

<div id="area"> 
    <p>City area:</p> 
    <%= f.collection_select(:area_id, [], :id, :name, {:prompt => "Select an Area"}, {:id => 'areas_select'}) %> 
    <br /> 
</div> 

<div id="neighborhood"> 
    <p>Neighborhood:</p> 
    <%= f.collection_select(:neighborhood_id, [], :id, :name, {:prompt => "Select a Neighborhood"}, {:id => 'neighborhoods_select'}) %> 
    <br /> 
</div> 

我知道我可以做的形式代碼類似Area.order（ '名ASC'），但我想讓它保持空白，直到城市被選中。

Answer 1

您可以設置爲了做這個：

@areas = city.areas.order("name asc").map{|a| [a.name, a.id]} 
@neighborhoods = Neighborhood.where(:area_id => city.areas.each{|a| a.id}).order("name asc").map{|s| [s.name, s.id]} 

而且在更新代碼：

@neighborhoods = area.neighborhoods.sort_by(&:name).map{|s| [s.name, s.id]}.insert(0, "Select a neighborhood")