Content classes

This is an introduction on how to use the core classes of Exponential at a low level. With these classes you can define what elements an object should be made up of. Content Class is the name of this definition.

Creating a Content Class

Before the system can be populated with actual content objects a class is needed. A class consists primary of a name, an identifier and a list of attributes. Classes like objects are versioned albeit in a minimalistic fashion. A class either is defined which means there is only one working copy, or it is a temporary meaning that it has just been created but is currently being worked on or it is modified which means that someone is working on a temporary version and a defined version is already exists.

Note: To make objects of a new class available to anonymous users you must edit the Anonymous role, as this role has specified access limitation by class by default.

Creating the class is done by calling the static create() function in eZContentClass, it takes one parameter which is the ID of the user creating the class. Usually this is the current user which is fetched with eZUser::currentUser(). Once the create() functions returns we have an eZContentClass object which is a temporary version and has creator, modifier and dates filled in. We then set the name and identifier ourselves.

include_once( "kernel/classes/ezcontentclass.php" );

// create new empty class
$user =& eZUser::currentUser();
$class = eZContentClass::create( $user->attribute( "id" ) );

// set the name and identifier
$class->setAttribute( "name", "new class1" );
$class->setAttribute( "identifier", "new_class1" );

The class is now ready to be stored, we call store() to store a temporary version.

$class->store();

To make the class more useful we must add some class attributes. Attributes are created in the same was as classes but take two parameters, the ID of the class and the stringname of the data type. For now we'll assume that a data type called ezstring exists. As you see we also set the name and identifier of the attribute.

$classAttribute = eZContentClassAttribute::create( $class->attribute( "id" ),
                                                   "ezstring" );
$classAttribute->setAttribute( "name", "new attribute1" );
$classAttribute->setAttribute( "identifier", "new_attribute1" );
$classAttribute->store();
// Add to attribute list
$classAttributes = array();
$classAttributes[] =& $classAttribute;

Now we're happy with our new class and want to make it appear as a defined class. We do that by removing the temporary version, setting the version to 0 and storing it.

// Remove this class and all it's attributes (note the true parameter)
$class->remove( true );
// Change version to defined, again for all attributes as well
// this also fetches a list of temporary attributes
$class->setVersion( 0, true );
// Alternatively
$class->setVersion( 0, $classAttributes );

// Finally store the class and all it's attributes
$class->store( $classAttributes );

Fetching the classes

Now that we've stored the class we can find it among the defined list. We do that by fetching classes which has version equal to 0. We will then get an array with eZContentClass objects.

// fetch all defined classes
$classes =& eZContentClass::fetchList( 0 );

Once we got the class list we can iterate over it and fetch the attributes and then print out the id of each attribute.

foreach( $classes as $class )
{
  // We must fetch the attributes ourselves, they do not get fetched automatically
  $classAttributes =& $class->fetchAttributes();
  foreach( $classAttributes as $classAttribute )
  {
    print( $classAttribute->attribute( "id" ) );
  }
}

Fetching a class directly can be done if the class ID is known. We then modify the class name and store it. It's very important to update the modification date, that it's easy for external clients to find out if an object has changed.

// Fetch class with ID 42 if it exists
$class =& eZContentClass::fetch( 42 );
if ( $class !== null )
{
  print( $class->attribute( "name" ) );
  $class->setAttribute( "name", "Some other name" );
  // Change modification date
  $class->setAttribute( "modified", eZDateTime::currentTimeStamp() );
  $class->store();
}