Run-Time Tree (Containers)

There are two relevant traits in the Container mechanics. Your “container” object should implement ContainerTrait and your child objects should implement TrackableTrait (if not, the $owner/$elements links will not be established)

If both parent and child implement AppScopeTrait then the property of AppScopeTrait::app will be copied from parent to the child also.

If your child implements InitializerTrait then the method InitializerTrait::init will also be invoked after linking is done.

You will be able to use ContainerTrait::getElement() to access elements inside container:

$object->add(new AnoterObject(), 'test');
$another_object = $object->getElement('test');

If you additionally use TrackableTrait then your objects also receive unique “name”. From example above:

  • $object->name == “app_object_4”
  • $another_object->name == “app_object_4_test”

Name Trait

trait ObjectTrait

Name trait only adds the ‘name’ property. Normally you don’t have to use it because TrackableTrait automatically inherits this trait. Due to issues with PHP5 if both ContainerTrait and TrackableTrait are using NameTrait and then both applied on the object, the clash results in “strict warning”. To avoid this, apply NameTrait on Containers only if you are NOT using TrackableTrait.


property ObjectTrait::$name

Name of the object.



Container Trait

trait ContainerTrait

If you want your framework to keep track of relationships between objects by implementing containers, you can use ContainerTrait. Example:

class MyContainer extends OtherClass {
    use atk4\core\ContainerTrait;

    function add($obq, $args = []) {
        return $this->_add_Container($obj, $args);

class MyItem  {
    use atk4\core\TrackableTrait;

Now the instances of MyItem can be added to instances of MyContainer and can keep track::

$parent = new MyContainer();
$parent->name = 'foo';
$parent->add(new MyItem(), 'child1');
$parent->add(new MyItem());

echo $parent->getElement('child1')->name;
// foo_child1

if ($parent->hasElement('child1')) {

$parent->each(function($child) {

Child object names will be derived from the parent name.


property ContainerTrait::$elements

Contains a list of objects that have been “added” into the current container. The key is a “shot_name” of the child. The actual link to the element will be only present if child uses trait “TrackableTrait”, otherwise the value of array key will be “true”.


Trackable Trait

trait TrackableTrait

Trackable trait implements a few fields for the object that will maintain it’s relationship with the owner (parent).

When name is set for container, then all children will derive their names of the parent.

  • Parent: foo
  • Child: foo_child1

The name will be unique within this container.


property TrackableTrait::$owner

Will point to object which has add()ed this object. If multiple objects have added this object, then this will point to the most recent one.

property TrackableTrait::$short_name

When you add item into the owner, the “short_name” will contain short name of this item.