Ruby on Rails Country/State Select Enigma

问题

I am trying to implement something seemingly very simple, and I have been beating my head against it for days at this point.

My desired end result is a Country select drop-down, tied to a State select drop-down, in such a way that when a given country is selected, IF states are known THEN those states are displayed in a select drop down, and if NO states are known for that country, then a text field is displayed instead.

I feel like I am almost there. At this point the interface will actually generate that list of states based on the persons' country, except it is refusing to update the drop-down dynamically.

The portion of my view where country and state location is gathered looks like:

# _person_setup.html.erb
         <td>
        <%= f.label :country, 'Select your country' %>*<br />
        <%= f.select :country, Carmen::country_names, {}, 
          {:style => 'width: 200px', 
          :id => 'country_select',
          :onchange => remote_function(
            :url => {:action => 'update_states'},
            :with => "'country='+value")} %>            
      </td><td>
        <p>
        <div id="states_div">
            <%= render :partial => 'states', 
                :object => Carmen::states(
                            Carmen::country_code(
                              @person.country)),
                :locals => {:form => f} %>
       </div>
        </p>            
      </td>

The partial being referenced in the DIV is as follows:

 # _states.html.erb
<% unless states.nil? or states.empty? %>
    <%= form.label :state, 'Select your state' %>*<br />
    <%= form.select :state, states.collect{|s| [s[0], s[0]]} %>
<% else %>
    <%= form.label :state, 'Please enter state or province' %>*<br />
    <%= form.text_field :state %>
<% end %>

Finally, the controller code which is intended to update the list of states dynamically:

def update_states    
puts "Attempting to update states..."    
q = params[:country]    
states = Carmen::states(Carmen::country_code(q))
puts "Country = #{q}, states = #{states.collect{|s| s[0]}.join(", ")}."
render :update do |page|
    page.replace_html "states_div", 
      :partial => 'states',
      :object => states,
      :locals => {:form => form_for(@person)}
end
puts "OK"
end

Now, this code is being called at the proper time and generating the appropriate lists of states. For example, when the user clicks Australia, "Attempting to update states... Country = Australia, states = Australian Capital Territory, New South Wales, Northern Territory, Queensland, South Australia, Tasmania, Victoria, Western Australia" shows up in the server process. However it doesn't update the page, and won't print the "OK" at the end. In short the line which is failing is undoubtedly

page.replace_html "states_div", 
      :partial => 'states',
      :object => states,
      :locals => {:form => form_for(@person)}

Note that replacing this line with

page.replace_html 'states_div', "<b>is it working</b>"

properly replaces the div, but of course not with anything useful.

Can someone help me understand what is going on here?

回答1:

It looks like you're assuming that the @person variable is still available from your original action. This could be set up by a filter for the current person but you don't show that in your question.

If you do need to lookup the @person again you'll have to pass the id through in your remote_function I think.

回答2:

Ryan Bates has a Railscast that shows how to select a category for a product or create a new category by typing the name. It sounds like a similar scenario to what you have, so you might want to check it out: Create Model Through Text Field.

回答3:

This took me a full day to figure out something that would at least "work". I am also using Carmen and also messing with the select tag in a form_for model form (actually, fields_for nested within forms_for...which adds additional complications).

I would think there is a better solution but this worked for me. The select needs to be referenced by the form but the options don't. Thus, first time through, I use the Carmen state_select method which populates the select tag correctly and all the nested options tags. The second time through, I just replace the options. Take a look:

In the view, I chose to use an observe_field method since I do other things besides update the states (some other localization changes) but this should work for remote_function and others, too:

<%= address_form.country_select :country, {:prompt => "--Select One--"} %>

Don't be confused by the id (user_address_attributes_country) it is just my silly forms_for/fields_for implementation)

<%= observe_field :user_address_attributes_country, :url => { :action => :changecountry }, :with => 'new_country' %>

<%= address_form.state_select :state, @user.address.country, {:prompt => "--Select One--"}, :style => 'width: 90px' %>

Then in my controller, it just looks like this:

def changecountry
  c = params[:new_country]

  respond_to do |format|
    format.html
    format.js {
      render :update do |page|
        page['user_address_attributes_state'].innerHTML = \
          "<option>--Select One--</option>" + state_options_for_select(nil, c)
      end
    }
  end
end

Note: state_options_for_select is also from Carmen. I could not get it to work unless I put it inside the respond_to block where I guess the view helpers are available. Also, I hard code user_address_attributes_state which is my nested id generated from the form_for/fields_for address_form.state_select rendering call in the view.

I hope this helps. If anyone can do it better, believe me, I'm all ears. I'll change the design in time...but needed something that just worked today and this was the best I could figure out in a limited time.

来源：https://stackoverflow.com/questions/976173/ruby-on-rails-country-state-select-enigma

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