Re: howto: strict or relaxed type checking?

Here's a good practice:  Leave the attribute constraint strict all the time, and 
provide a coersion functionality to examine the raw input and reformat it from 
the variety of formats there might be so that it either matches the strict 
definition or fails because it can't be converted. -- Darren Duncan

Heiko Jansen wrote:
> Guys,
> 
> I´m trying to implement a Moose-based module for objects according to
> some standard.
> 
> The standard tells us, that the objects may have a fixed set of
> attributes with a defined structure.
> 
> There is, for example, a "date" attribute which should conform to "YYYY-MM-DD".
> So as a simple first approach I defined an attribute "date" having as
> type a subtype of Str which conforms to the regex
> /\A(1[4-9]|20)\d\d-\d\d-\d\d\Z/. (Not very sophisticated, but probably
> enough for this mail).
> 
> Now on one hand I want to make sure that the objects we create in our
> software are valid.
> 
> On the other hand we see non-standard-compliant attribute values (e.g.
> "12/01/1980" for "date") in incoming requests so that type checking
> fails when parsing these requests.
> 
> However, I don´t want the parsing to fail in most cases, because the
> quality of results computed over the inaccurate data will likely
> degrade but not be completely useless.
> 
> So I´m looking for a way to switch on either strict or relaxed type
> checking but I don´t know how.
> 
> The only solution I could think of was looking at a package-global
> variable within the type checking code:
> 
> ... where { if ($PKG::STRICTMODE) { $_ =~
> /\A(1[4-9]|20)\d\d-\d\d-\d\d\Z/ } else {1} };
> 
> But I´d rather like to make the decision within an object scope like so:
> 
> Pack::MyClass->new( strict => 0 )->parse( $uri );
> 
> I haven´t got much experience using Moose and am hoping for someone to
> share her/his experience on solutions considered good practice.
> 
> Thx.!
> Heiko
>