控制器没有从laravel的路线获得id

am developing one php application using laravel. in that when i trying to pass value from view to controller using ajax call. am having a issue in routing this is my code in routing

  Route::post('AssetdetailsController/postPositions/{id}', array('as'=>'post_form','uses' => 'Controllers\Admin\AssetdetailsController@postPosition'));

am trying to pass the route value in javascript alert am getting an empty alert box.

This is my ajax call

$(document).ready(function() { 
    $('#asset_type_id').change(function() {
        // alert($('#asset_type_id option:selected').val());
        var id = $('#asset_type_id option:selected').val();     
        $.ajax({
            type: 'POST',
            url: '{{ URL::route('post_form') }}',
            data: id,
            cache: false,
            success: function(data)
            {
            alert(data);
                check(data);
            },
            error: function(xhr, textStatus, thrownError) {
                alert('Something went to wrong.Please Try again later...');
            }
        });
    });
});     

This is my controller

public function postPosition($id)   {

            $positions = DB::table('asset_types')->where('id', '=', $id )->pluck('is_nesd');

            return  $positions;

    }

I tried like this to check the value that i am getting in id through alert box

public function postPosition($id)   {

                return  $id;

        }

I got output as {id} in alert box.

I also tried passing a value manually in query instead of ${id} and iam getting the correct output

 public function postPosition($id)  {

                $positions = DB::table('asset_types')->where('id', '=', 1 )->pluck('is_nesd');

                return  $positions;

        }

So now my question is how get the value of ${id} correctly from view.

Hi i finally get the answer what i did is

In ajax function my old code is

  url: '{{ URL::route('post_form') }}', 

And i changed to

 url:  '{{ action("postPositions", " ") }}'+id,

This one working correctly