Rails grouped_collection_select与3个模型

Question

我试图按照Rails Docs和Railscast＃88，但有3个模型。该页面将有3个下拉框供州，县，&城市使用。我有State> County使用JQuery。但是当试图为城市建造grouped_collecion_select事情正在破裂。

这里有3种型号：

service_area_state.rb

class ServiceAreaState < ActiveRecord::Base 
    has_many :service_area_counties 
    default_scope -> { order(name: :asc) } 
end 

service_area_county.rb

class ServiceAreaCounty < ActiveRecord::Base 
    belongs_to :service_area_state 
    default_scope -> { order(name: :asc) } 
end 

service_area_city.rb

class ServiceAreaCity < ActiveRecord::Base 
    belongs_to :service_area_county 
end 

在我的控制，我有以下几点：

def index 

    @states = ServiceAreaState.all 
    @counties = ServiceAreaCounty.all 
    @cities = ServiceAreaCity.all 

end #index 

在视图中我有：

index.html.erb

<div class="row"> 
<div class="field" id='state_div'> 

    <%= label_tag :service_area_state_id, "State", id:"service_area_state" %> <br/> 

**This works** 
    <%= collection_select(:service_area_state, :id, @states, :id, :name, prompt: true) %> 

</div> 

<div class="field" id='county_div'> 
    <%= label_tag :service_area_county_id, "County" %><br> 

**This works** 
    <%= grouped_collection_select(:service_area_county, :service_area_county_id, @states, :service_area_counties, :name, :id, :name, prompt: true) %> 
</div> 

<div class="field" id='city_div'> 
    <%= label_tag :service_area_city_id, "City" %><br> 

**This does not work** 
    <%= grouped_collection_select(:service_area_city, :service_area_county_id, @counties, :service_area_cities, :name, :id, :name, prompt: true) %> 
</div> 
</div> 

我得到以下错误：

undefined method `service_area_cities' for #<ServiceAreaCounty:0x007fb5e7dac060> 

在此行中：

<%= grouped_collection_select(:service_area_city, :service_area_county_id, @counties, :service_area_cities, :name, :id, :name, prompt: true) %> 

能

有人点我哪里错了？

谢谢！

Answer 1

您需要设置service_area_cities作为ServiceAreaCounty模型的关联（听起来就像是一个的has_many协会）：

class ServiceAreaCounty < ActiveRecord::Base 
    belongs_to :service_area_state 
    has_many :service_area_cities 
    default_scope -> { order(name: :asc) } 
end