Validation messages and $.parseJSON(xhr.responseText).errors

[akvarel]

Hello!
I try to catch a validation message with a

`$.parseJSON(xhr.responseText).errors`

but an allert message hows me "undefined" and I dont understand why.

hier are my validations:

validates :upload_file_name,  :presence   => true,
                                    :format     =>{:with => %r{\.(jpg)$}i,:message =>"It should be a pdf File"}
                                    
      validates_uniqueness_of :upload_file_name, :message => "blabla"
     
      validates :upload_file_size,  :inclusion  => {:in =>1.megabytes..20.megabytes,:message=>"bla"}

json:

format.json{ render json: {error: @upload.errors.full_messages}, :status =>422}

and javascript for that:

$('#fileupload').fileupload({       
    
    
            error: function(xhr){
              var errors = $.parseJSON(xhr.responseText).errors
              alert(errors)         
            }
                  });

Thanks in advanced