[Dancer-users] Multiple "optional" components in URLs

Ovid curtis_ovid_poe at yahoo.com
Thu Apr 19 12:51:41 CEST 2012

Hi all,

I had this in my Dancer code:

  get '/instance/?:id?' => sub {
      my $id = param('id');

That let's me do this:

  http://localhost:5000/instance      # get a list of instances
  http://localhost:5000/instance/     # get a list of instances

  http://localhost:5000/instance/213  # get instance 213

However, after I typoed a URL, I discovered that it would also match:

  http://localhost:5000/instances     # get instance 's'

This is because of the generated regex:


I've fixed this by switching to regex paths, but I would argue for the following to be the regex generated from my example above:


In other words, if you have multiple "optional" components in a path, they are all required up to, but excluding, the last optional component found in the URL that is accessed. You could then safely visit /instance, /instance/, and /instance/42.

This would allow the easy construction of things like this:


Allowing you to access:


This would make it easy to write the sort of URLs that I often write.

Speculation: at that point, if we have an optional component, we could *assume* that the preceding / must be optional (?), leading to a simple URL:


Once something optional is found, nothing after it may be mandatory (otherwise, if you had optional items collapsing out of the URL, it would be a semantic mess that's impossible to sort through).


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