Rails change boolean value with checkbox and jquery ajax

As of Rails 4, there's a way to do this without needing any additional JS or CSS:

<%= check_box_tag 'completed', task.id, task.completed,
      data: {
        remote: true,
        url: url_for(action: :toggle, id: task.id),
        method: "POST"
      } %>

It turns out that adding remote: true to an input causes jquery-ujs to make it ajax-y in all the nice ways. Thoughtbot's "A Tour of Rails jQuery UJS" briefly touches this (and many other good things available); the "Unobtrusive scripting support for jQuery" page in the jQuery UJS wiki does a thorough job on this as well.

Try the following (leaving everything else as is):

the javascript:

$(".task-check").bind('change', function(){
  if (this.checked){
    $.ajax({
      url: '/todos/'+this.value+'/toggle',
      type: 'POST',
      data: {"completed": this.checked}
    });
  }
  else {
     alert("no");
  }
});

the controller:

def toggle
  @task = Todo.find(params[:id])

  if @task.update_attributes(:completed => params[:completed])
    # ... update successful
  else
    # ... update failed
  end
end

Take a look at bundle exec rake routes to show you the paths that rails generates. In the case of your post 'toggle' which is a member you get a path like /todos/:id/toggle, hence the updated url in the ajax.

In the controller the :id from the path ends up in params[:id]. The data from the ajax request also ends up in the params hash, hence params[:completed].