Is it possible to put just a rails form element in a partial?

问题

My app has a select box for users to choose a "venue". This select box is, as you would expect, in a form. I also have an action somewhere on the page that creates a new venue via AJAX. After the new venue is created, I would like to updated the venue select box to reflect this.

My solution was to put the select box in a partial and render the partial from the create action in the controller.

 <div id="venue_select" style="clear: both;">
    <%= render :partial => 'venue/venue_select_box' %>
 </div>

The partial looks like this:

<%= f.collection_select :venue_id, @user_venues, :id, :name, :prompt => 'Select a venue' %>

where f is the form reference:

<% form_for :shows do |f| %>

The problem is that f is undefined in the partial, so I get an error. One solution would be to include the entire form, but I feel like that should not be necessary because I am not updating the entire form. Any ideas on how to go about this?

回答1:

You can pass a variable to the partial like this:

  <%= render :partial => 'venue/venue_select_box', :locals => { :f => f } %>

For stuff like this it is always good to look at the documentation.

EDIT: To use the partial with AJAX request you'll need to "recreate" the form in your .rjs template. So in your controller you'll need to find the object again.

 def venue_select
    @venue = Venue.find(params[:id])
    respond_to do |format|
      format.html
      format.js
    end
 end

Then in your venue/venue_select.rjs file:

 form_for @venue do |f|
   page[:element].replace_html :partial => 'venue/venue_select_box', :locals => { :f => f }
 end

Where :element is the id of the select menu you want to replace. Basically you just recreate the form_for and then use that to update the select field.

回答2:

It might be easier to add the venue to the selectbox with Javascript, as an onComplete hook on your AJAX add.

回答3:

I agree with Sarah Mei on this, if anything have your AJAX call return a JSON representation of the venue that was added and then create a new option and add it to the select element.

Some general JS code for adding a select option:

var newOption = new Option("Text", "Value");
selectElement.options[selectElement.options.length] = newOption;

回答4:

These are all great options but I think I found the easiest. Basically, I just hard coded the name in the collection_select so I would not need the "f" variable:

<%= collection_select 'shows[venue_id]', :venue_id, @user_venues, :id, :name, { :prompt => 'Select one of your previous venues' } %>

Then my VenueController is as follows:

class VenueController < ApplicationController
  layout 'main'
  before_filter :login_required, :get_user

  def create
    begin
      venue = @user.venues.create(params[:venue])
      @user_venues = @user.venues
      render :partial => 'venue_select_box', :success => true, :status => :ok
    rescue ActiveRecord::RecordInvalid => invalid
      flash[:errors] = invalid.record.errors
      render :text => '', :success => false, :status => :unprocessable_entity
    end
  end

end

If this method is bad practice for any reason, please let me know and I will happily credit you for the answer.

回答5:

I think that your solution is not bad, but If you try to use this partial in another form you have a problem with the name of the field generated.

To avoid this you can submit within the ajax call the content of f.object_name. In your case it will be "shows" and because the method is :venue_id the generated name will be "shows[venue_id]".

来源：https://stackoverflow.com/questions/724045/is-it-possible-to-put-just-a-rails-form-element-in-a-partial