[Dancer-users] Input-validation and Error-Handling in a fun 'dancer' way

[Assaf Gordon]

Hello Dancers,

I have another dancer-newbie question:

Is there a recommended way to verify input (or general variables) and report errors to the user ?

Common scenario:
I have a form with 3 inputs, and they need to by in a certain format (verifiable by a simple regex).
If the inputs do not conform, I want to:

1. Log the error for later inspection
2. Inform the user (e.g. using Plugin::Dancer::FlashMessage)
(The error message reported to the user is not necessarily the same one written to the log, if I wish to include more technical details in the log, or be more descriptive and verbose to the user).
3. Stop processing the request.

And I wish to do it in the most 'fun' dancer kind of way.

Looking at a naive implementation (below), there's alot of redundant code for validating and reporting the error back to the user (and more validation code than actual processing code).

Any suggestions ?

Thanks!
 -gordon


====================

post '/dosomething' => sub {
    my $email = params->{email};
    my $gene = params->{gene};
    my $cutoff = param->{cutoff};

     if (!defined $email) {
	warning "Missing email address";
        flash error => 'Missing email address';
        return template 'form_errors' ;
    }
    elsif (!valid_email($email)) {
	warning "Got Invalid email address: $email";
        flash error => 'Invalid email address";
        return template 'form_errors' ;
    }

    if (!defined $gene) {
	warning "Missing gene identifier";
        flash error => 'Missing gene identifier';
        return template 'form_errors' ;
    }
    elsif (!valid_gene_identifier($gene)) {
	warning "Got Invalid gene identifier: $gene";
        flash error => 'Invalid gene identifier";
        return template 'form_errors' ;
    }

    if (!defined $cutoff) {
	warning "Missing cutoff identifier";
        flash error => 'Missing cutoff identifier';
        return template 'form_errors' ;
    }
    elsif (!valid_cutoff_value($cutoff)) {
	warning "Got Invalid cutoff value: $cutoff";
        flash error => 'Invalid Cutoff value: must a value between 0.1 and 0.55';
        return template 'form_errors' ;
    }

    ## Input IS OK, do some processing and return the result
    my ($result, $error) = process($email, $gene, $cutoff);

    template 'result.tt', {
          email => $email,
          cutoff => $cutoff,
          gene  => $gene,
          result => $result,
          error => $error,
    };
}