Dancer2: fetching nested data from hash stored in YAML session

Question

I'm using Dancer2 and the YAML session engine. I stored a complete hash in a session with the following code:

post '/login' => sub {
    # ...
    my $userdata = {
        fname => 'John',
        lname => 'Doe',
        uid => 1234,
    };
    # ...
    session userdata => $userdata;
    # ...
}

The omitted code checks the login data against a database and returns that $userdata hashref. This code creates a session file under $appdir/sessions with this content:

session file

userdata:
  fname: John
  lname: Doe
  uid: 1234

How can I retrieve single values from this session in my app.pm file? It works great in the template files (*.tt) and <% session.userdata.fname %> yields John, as expected. However, I want to fetch the first name in app.pm, like so:

get '/userdetails' => sub {
    my $firstname = session('userdata.fname'); # gives undef
    # do sth. with $firstname
}

Is that feasable? Or do I have to

my $userdata = session('userdata'); # fetch complete hash
# do sth. with $userdata->{fname}

I tried

• session('userdata.fname')
• session('userdata/fname')
• session('userdata:fname')
• session('userdata fname')
• RTFM (YAML's and Dancer2's)

but none of them worked and gave undef. The manuals and tutorials only fetch "first level values", not nested ones.

Answer 1

The Template Toolkit syntax is completely independent of Perl Dancer2, and you should expect any form of addressing to carry over. The origin of the data as a YAML file is also irrelevant, as the Dancer session is just a Perl hash structure

The manual doesn't make it very clear, but

session('userdata')

is the same as

session->{userdata}

So you can use

session->{userdata}{fname}

to read the subsidiary fields

(Or possibly session('username')->{fname} if you prefer, but that looks a bit icky to me!)

Note that you shouldn't use the YAML session engine in production code, as it's very slow