[Templates] Views in Template Toolkit

[Andy Wardley]

Hi Noah,

> The "view" feature of TT, discussed in Chapter 3, left me excited but 
> questioning why it's so limited. If different views can be provided for 
> hashes, arrays, and scalars, why stop there?

...because the example in the book was just a brief introduction to views,
not an extensive discussion of them.

> The views should be 
> declared based on class name, so an object of class "A::Beta" could have 
> a different dynamic view from "A::Gamma" without any extra work on the 
> programmer's part.

Yep, that's exactly what they do.  From the documentation:

   http://tt2.org/docs/manual/Views.html#section_Views_as_Data_Presenters

   You can also provide templates to print objects of any other class. The
   class name is mapped to a template name with all non-word character
   sequences such as '::' converted to a single '_'.

   [% VIEW foo %]
      [% BLOCK Foo_Bar %]
         a Foo::Bar object:
             thingies: [% view.print(item.thingies) %]
              doodahs: [% view.print(item.doodahs)  %]
      [% END %]
   [% END %]


> Can anyone comment on the purpose and value of views, with respect to 
> this reviewer's question?

The views reviewer should first review the views documentation.  :-)

Views are an incredibly useful feature for a particular class of problem.
If you have a nested data structure of some kind (e.g. XML DOM) that you
want to transform using templates, then views are definitely worth a look.

They're officially experimental in TT2, largely because the particular
syntax I chose and a few of the internal details are likely to change in
the future (TT3).  But that doesn't mean that they're not fully-formed
and functional.

A colleague on a recent project (using TT views to transform generic XML
to various different device-specific markup formats for mobile browsing)
described them thusly:

   TT + VIEWS eq XSLT on crack


HTH
A