Class yii\di\Instance

Instance represents a reference to a named object in a dependency injection (DI) container or a service locator.

You may use get() to obtain the actual object referenced by $id.

Instance is mainly used in two places:

• When configuring a dependency injection container, you use Instance to reference a class name, interface name or alias name. The reference can later be resolved into the actual object by the container.
• In classes which use service locator to obtain dependent objects.

The following example shows how to configure a DI container with Instance:

$container = new \yii\di\Container;
$container->set('cache', [
    'class' => 'yii\caching\DbCache',
    'db' => Instance::of('db')
]);
$container->set('db', [
    'class' => 'yii\db\Connection',
    'dsn' => 'sqlite:path/to/file.db',
]);

And the following example shows how a class retrieves a component from a service locator:

class DbCache extends Cache
{
    public $db = 'db';

    public function init()
    {
        parent::init();
        $this->db = Instance::ensure($this->db, 'yii\db\Connection');
    }
}