Passing variable value form js function to rails view (dynamic select)

I use Ryan's method to add and remove nested model fields dynamically through JavaScript using jQuery.

There are 4 models: client, c_person; project, p_person. And one-to-many associations: client has many c_people and project has many p_people (these are people from client's side but they belongs to project).

So, I have following problem:

When I use helper method "link_to_add_fields" in my view, I need to pass another parameter (current_client_id) that depends on what client is currently selected in select box.

<!-- new.html.erb -->
<p>
<%= f.label :client_id %></br>
<%= f.collection_select :client_id, Client.order("title"), :id, :title %>
</p>
<p>
<%= f.fields_for :p_people do |builder| %>
<%= render "p_person_fields", :f => builder %>
<% end %>
</p>
<p&开发者_运维技巧gt;<%= link_to_add_fields "Add Person", f, :p_people, current_client_id %></p>

I need that to dynamically change the collection for @people variable in helper method,

# application_helper.rb
def link_to_add_fields(name, f, association, current_client_id)
    new_object = f.object.class.reflect_on_association(association).klass.new
    @people = CPerson.where(:client_id => current_client_id).order(:name) unless current_client_id.blank?
    fields = f.fields_for(association, new_object, :child_index => "new_#{association}") do |builder|
      render(association.to_s.singularize + "_fields", :f => builder)
    end
    link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")"))
end

to finally use it in partial:

<!-- _p_person_fields.html.erb -->
<div class="fields">
<p>
<%= f.collection_select :content, @people, :name, :name %>
<%= f.hidden_field :_destroy %>
<%= link_to_function "Remove", "remove_fields(this)" %>
</p>
</div>

Here is simple js function to get current_client_id value, but I don't know how to pass it to my view or helper method.

// application.js
function current_client_id() {
var current_client_id = $("select#client_id :selected").val();
}

I appreciate your help! Maybe there is a better solution?

One thing I don't like about this is that you're using logic in a view helper that really belongs in your controller.

Maybe a better approach would be to make an AJAX call to a controller with the current_client_id. That controller can then get the @people object and send back a js.erb template where you can append a partial to your view. Or it could send back a JSON object and the handler to your AJAX call will create new elements to add to the DOM.

I've found the better way to assign people to the project – use multiple select option. This allows not to use nested model fields.

1.Use has_and_belongs_to_many association between two models: c_person and project.

2.Create join table:

class CreateCPeopleProjects < ActiveRecord::Migration
  def self.up
    create_table :c_people_projects, :id => false do |t|
      t.references :project
      t.references :c_person  
    end  
  end

  def self.down
    drop_table :c_people_projects
  end
end

3.Modify new.html.erb and the partial.

<!-- new.html.erb -->
<p>
<%= f.label :client_id, "Client" %><br />
<%= f.collection_select :client_id, @clients, :id, :title %>
</p>
<div id="people">
<%= render "c_people" %>
</div>

<!-- _c_people.html.erb -->
<p>
<%= fields_for :project do |f| %>
 <% if @update_people.blank? %>
 <%= f.collection_select :c_person_ids, @people, :id, :name, {:selected => @project.c_person_ids}, {:multiple => true, :name => "project[c_person_ids][]"} %>
 <% else %>
 <%= f.collection_select :c_person_ids, @update_people, :id, :name, {}, {:multiple => true, :name => "project[c_person_ids][]"} %>
 <% end %>
<% end %>
</p>

4.Add js function to get current client id value, send it to projects_controller and replace partial with new collection.

jQuery(function($) {
 $(function() {
  $("#project_client_id").change(function() {
  var client_id = $("select#project_client_id :selected").val();
  if (client_id == "") {client_id = "0";}
  $.get("/projects/update_people/" + client_id, function(data){
   $("#people").html(data);
  })
  return false;
  });
 });
})

5.Add method to projects_controller to dynamically change the collection for people. And one line to update action (for updating nil objects).

  def update
    @project = Project.find(params[:id])
    params[:project][:c_person_ids] ||= []

    respond_to do |format|
      if @project.update_attributes(params[:project])
        format.html { redirect_to(@project, :notice => 'Project was successfully updated.') }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @project.errors, :status => :unprocessable_entity }
      end
    end
  end

  def update_people
    @update_people = CPerson.where(:client_id => params[:id]).order(:name) unless params[:id].blank?
    render :partial => "c_people"
  end

6.Don't forget about the routes: match "/projects/update_people/:id" => "projects#update_people"

If you are using Rails 3, then you should remove "h(" in application_helper.rb :

link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")"))

to

link_to_function(name, "add_fields(this, \"#{association}\", \"#{escape_javascript(fields)}\")")