[dancer-users] session() auto-flush

Naveed Massjouni naveedm9 at gmail.com
Fri Feb 14 08:16:15 GMT 2014

On Thu, Feb 13, 2014 at 11:37 PM, Warren Young <warren at etr-usa.com> wrote:
> I tried passing the return value of session() into a function in another
> module which purposely does not "use Dancer".  Thus, I cannot use the global
> DSL functions without explicit qualification.
> This other module modifies the session object, so the code looked something
> like this:
> package App::Helper;
> sub do_something_interesting {
>     my ($session) = @_;
>     $session->{foo} = 'bar';
>     # ... and lots more like that
> }
> To my surprise, I found that in the calling route handler...
> get '/myroute' => sub {
>     do_something_interesting(session());
>     session 'more' => 'changes here';
> }
> ...the changes to the session object made by the helper module got lost.
> I finally tracked it down to the fact that session(X, Y) automatically calls
> flush() on the object for you, whereas session() with no parameters returns
> a hashref that doesn't auto-flush itself.
> On one level, I guess live and learn.  But, is it good design for Dancer to
> simply forget all my changes?  Why doesn't the second line in my route
> handler simply continue to modify the in-memory session object, and flush
> all the changes at once?

It does not make sense to me that calling session() as a getter (as
opposed to a setter) should write out the session on each access. To
do that would probably require using Tie::Hash to have it invoke
flush() on every modification of the hash. I'm not sure if that extra
complexity is worth the benefit.

-Naveed Massjouni

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