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Fetch functions

Let templates fetch your data: function_definition.php, the collection class and its result array, a verified example, fetch aliases, and extended attribute filters for content fetches.

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Address: https://doc.exponential.earth/exphelp/viewer/help/extension-development/part-3-extension-developer/fetch-functions.md

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Fetch functions

Part 3, chapter 14. fetch( 'content', 'list', ... ) is a fetch function of the module content. Your module can offer its own: fetch( 'hello', 'newest', hash( 'class_identifier', 'article' ) ). Fetch functions are the right way to give templates data that needs PHP, without putting logic in templates. The engine is eZFunctionHandler and eZModuleFunctionInfo (lib/ezutils/classes/).

Where it lives

A fetch function belongs to a module, so your extension needs a module folder registered with ExtensionRepositories[] (Modules and views). The module may have no views at all; then it exists only for its fetch functions.

extension/mysite_hello/
    modules/hello/function_definition.php
    classes/mysitehellofunctioncollection.php

function_definition.php 

<?php
$FunctionList = array();

$FunctionList['newest'] = array(
    'name' => 'newest',
    'call_method' => array( 'class' => 'mysiteHelloFunctionCollection',
                            'method' => 'fetchNewest' ),
    'parameters' => array(
        array( 'name' => 'class_identifier', 'type' => 'string', 'required' => true ),
        array( 'name' => 'parent_node_id', 'type' => 'integer', 'required' => false, 'default' => 2 ),
        array( 'name' => 'limit', 'type' => 'integer', 'required' => false, 'default' => 5 )
    )
);

The parameters are passed to the method in the order listed, matched by name from the template's hash(); missing optional ones get their default. The eztags extension's modules/tags/function_definition.php is a larger real example.

The collection class 

<?php
/**
 * Fetch functions of the module "hello":
 *   fetch( 'hello', 'newest', hash( 'class_identifier', 'article', 'limit', 3 ) )
 */
class mysiteHelloFunctionCollection
{
    public static function fetchNewest( $classIdentifier, $parentNodeID = 2, $limit = 5 )
    {
        $limit = max( 1, min( (int)$limit, 50 ) );
        $nodes = eZContentObjectTreeNode::subTreeByNodeID(
            array( 'ClassFilterType' => 'include',
                   'ClassFilterArray' => array( (string)$classIdentifier ),
                   'SortBy' => array( 'published', false ),
                   'Limit' => $limit ),
            (int)$parentNodeID
        );
        return array( 'result' => is_array( $nodes ) ? $nodes : array() );
    }
}

The method returns an array with the key result; the engine hands result to the template (eZModuleFunctionInfo::execute(): no result key is reported as "did not return a result value"). Return array( 'result' => false ) for "nothing found", the convention the eztags collection uses. Called with the kernel loaded on sample content, the method above returned the three newest nodes of the class it was given.

subTreeByNodeID() applies the current user's read permissions, like every content fetch; so does your function.

Using it 

{def $newest = fetch( 'hello', 'newest', hash( 'class_identifier', 'article', 'limit', 3 ) )}
{foreach $newest as $node}
    {node_view_gui content_node=$node view='line'}
{/foreach}
{undef $newest}

Fetch aliases

fetchalias.ini gives a short name to a fetch with fixed parameters, used with fetch_alias():

[newest_articles]
Module=hello
FunctionName=newest
Constant[class_identifier]=article
Constant[limit]=3
{def $newest = fetch_alias( 'newest_articles', hash() )}

The kernel's settings/fetchalias.ini documents the format and ships examples ([object], [news_list]).

Extended attribute filters

Sometimes the content fetches (list, tree) are right but need one more SQL condition, for example a join with your own table. An extended attribute filter adds tables, joins and columns to them:

# extension/mysite_hello/settings/extendedattributefilter.ini.append.php
[MysiteRatedFilter]
ExtensionName=mysite_hello
FileName=classes/mysiteratedfilter.php
ClassName=mysiteRatedFilter
MethodName=createSqlParts
<?php
class mysiteRatedFilter
{
    public function createSqlParts( $params )
    {
        $minimum = isset( $params['minimum'] ) ? (int)$params['minimum'] : 0;
        return array(
            'tables' => ', mysite_rating r',
            'joins'  => " r.contentobject_id = ezcontentobject.id AND r.score >= $minimum AND ",
            'columns' => ''
        );
    }
}
{fetch( 'content', 'list', hash( 'parent_node_id', 2,
                                  'extended_attribute_filter', hash( 'id', 'MysiteRatedFilter',
                                                                     'params', hash( 'minimum', 4 ) ) ) )}

The kernel calls createSqlParts( $params ) and inserts tables, joins and columns into its query (createExtendedAttributeFilterSQLStrings() in kernel/classes/ezcontentobjecttreenode.php). Everything you put in the SQL must be safe: cast numbers, escape strings with eZDB::instance()->escapeString().

RAD

Template extension (/setup/templateoperator) writes fetch functions with their definition and collection class; see With RAD: a template operator in five minutes.

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