Register custom predefined property

This example shows how to register a custom predefined property in Semantic MediaWiki with the convention that for the property key __ as leading identifer should be used to distinguish them from those defined by Semantic MediaWiki itself.

SMW::Property::initProperties

use Hooks;
use SMW\PropertyRegistry;

Hooks::register( 'SMW::Property::initProperties', function ( PropertyRegistry $propertyRegistry ) {

    // Canonical label
    define( 'PROP_LABEL_FOOBAR_KEY', 'Foobar key' );

    $definitions = [
        '__foobar_key' => [
            'label' => PROP_LABEL_FOOBAR_KEY,

            // Can contain default or custom datatypes (see
            // how to register custom datatypes)
            'type'  => '_txt',

            // MW message key
            'alias' => 'foobar-property-alias-key',

            // Is viewable on the facbox
            'viewable' => true,

            // Can be used by a user to create an annotation
            'annotable' => true
        ]
    ];

    foreach ( $definitions as $definition ) {

        $propertyRegistry->registerProperty(
            $propertyId,
            $definition['type'],
            $definition['label'],
            $definition['viewable'],
            $definition['annotable']
        );

        $propertyRegistry->registerPropertyAlias(
            $propertyId,
            wfMessage( $definition['alias'] )->text()
        );

        $propertyRegistry->registerPropertyAliasByMsgKey(
            $propertyId,
            $definition['alias']
        );
    }

    return true;
};