[Rails] Validation messages and $.parseJSON(xhr.responseText).errors

Hello!

I try to catch a validation message with a
`$.parseJSON(xhr.responseText).errors` but an alert message hows me
"undefined" and I do not 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