This is how you use autocomplete with jQuery Tokeninput and ActsAsTaggableOn.
In my situation i am using a nested form but it shouldnt matter. Everything below is code that works.
Code
Product Model:
attr_accessible :tag_list # i am using the regular :tag_list
acts_as_taggable_on :tags # Tagging products
Products Controller:
  #1. Define the tags path
  #2. Searches ActsAsTaggable::Tag Model look for :name in the created table.
  #3. it finds the tags.json path and whats on my form.
  #4. it is detecting the attribute which is :name for your tags.
def tags 
  @tags = ActsAsTaggableOn::Tag.where("tags.name LIKE ?", "%#{params[:q]}%") 
  respond_to do |format|
    format.json { render :json => @tags.map{|t| {:id => t.name, :name => t.name }}}
  end
end
Routes:
# It has to find the tags.json or in my case /products/tags.json
get "products/tags" => "products#tags", :as => :tags
Application.js:
$(function() {
  $("#product_tags").tokenInput("/products/tags.json", {
    prePopulate:       $("#product_tags").data("pre"),
    preventDuplicates: true,
    noResultsText:     "No results, needs to be created.",
    animateDropdown:   false
  });
});
Form:
<%= p.text_field :tag_list,
                 :id => "product_tags",
                 "data-pre" => @product.tags.map(&:attributes).to_json %>
Issue 1(SOLVED)
Must have the line:
format.json { render :json => @tags.collect{|t| {:id => t.name, :name => t.name }}}
Note - You can use @tags.map here as well and you dont have to change the form either.
Below are the 2 issues on why you needed to do this:
I have the following Tag: {"id":1,"name":"Food"}. When I save a Product, tagged "Food", it should save as ID: 1 when it searches and finds the name "Food". Currently, it saves a new Tag with a new ID that references the "Food" ID, i.e. {"id":19,"name":"1"}. Instead, it should be finding the ID, showing the name, and doing a find_or_create_by so it doesn't create a new Tag.
Issue 2(SOLVED)
When I go to products/show to see the tags by doing <%= @product.tag_list %>. The name appears as "Tags: 1", when it really should be "Tags: Food".
How can I fix these issues?
 
     
     
     
     
     
     
     
     
    