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<h1>ClearPress Framework</h1>
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<h2>Views</h2>
<p>
Views inherit and extend functionality of the ClearPress::view
superclass. At the very minimum, application views can contain as
little as no code, just the reference to their superclass for
inheritance purposes.
<code>package Grandkids::view::kid;
use strict;
use warnings;
use base qw(ClearPress::view);
1;
</code>
</p>
<p>
The superclass defines all of the basic functionality to support
extended CRUD mechanisms (create, read, update, delete, list, edit,
add) for XML, JSON, HTML and AJAX/HTML fragments.
</p>
<p>
Whilst basic functionality gets you part-way there it's often not
quite enough for more complicated scenarios. To take care of these
situations any method implemented in the view with the right
systematic name will override the method of the same name in the
superclass, e.g. list, list_xml, read, read_png, create_json etc.
</p>
<p>
Within these methods it is possible to access all of the useful bits
for processing a request and buildig a response.
</p>
<h3>Accessing CGI</h3>
<p>
When processing a web request it's usually handy to have any CGI
parameters. To get hold of them grab the instance of CGI.pm:
<code>sub list {
my $self = shift;
my $util = $self->util;
my $cgi = $util->cgi;
...
}</code>
</p>
<h3>Accessing the data model</h3>
<p>
Almost all requests need to do something with one or more data models
so at the very least you'll need to locate the one corresponding to
this view method before you do something with it:
<code>sub list {
my $self = shift;
my $model = $self->model;
...</code>
</p>
<h3>Putting it together</h3>
<p>
Let's say you have a small cascade of related objects, let's say a
family with a child, which need to be built from the results of a
POSTed form and saved together in one transaction. Assuming we're in
<i>Grandkids::view::family</i>...
<code>sub create {
my $self = shift;
my $util = $self->util;
my $cgi = $util->cgi;
my $family = $self->model;
my $f_name = $cgi->param('name');
$family->name($f_name);
my $c_name = $cgi->param('child_name');
my $child = Grandkids::model::child->new({name => $c_name});
$family->children($child);
return $family->create();
}</code>
This makes quite a lot of other assumptions too - the form posting to
this code has to contain both <i>name</i> and <i>child_name</i>
fields, and only one of each and the family model's <i>create</i>
method needs to check for children to save as part of its
transaction.
</p>
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