Which type do you use in an Extbase model for a property that holds several related objects, e.g. all speakers of a conference?

For 1:n and m:n relations Extbase uses the class ObjectStorage, e.g. protected ObjectStorage $speakers; with the annotation @var ObjectStorage<Speaker> for the IDE and static analysis. Entries are added through methods such as addSpeaker(), which call attach() internally, and removed with detach(). In the template you iterate the relation with <f:for each="{conference.speakers}" as="speaker">. The ObjectStorage must be initialised before it is accessed, otherwise an error occurs. PHP's SplObjectStorage looks similar, but Extbase cannot load relations into it or persist changes to it.