Saving and retrieving EntityAutocomplete value

Question

I'm building a block plugin that allows users to specify a menu to appear in a block plugin. I'm taking advantage of the EntityAutocomplete form element.

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Entity%21Element%21EntityAutocomplete.php/class/EntityAutocomplete/8.2.x

Here is how the form is built.

public function blockForm($form, FormStateInterface $form_state) {
    $form['menu'] = [
        '#type'          => 'entity_autocomplete',
        '#target_type'   => 'menu',
        '#default_value' => $this->configuration['menu'],
    ];
    return $form;
}

It's able to display the form element just fine. And it allows users to select menus as well. I then save the item on submit like this.

public function blockSubmit($form, FormStateInterface $form_state) {
    $this->configuration['menu'] = $form_state->getValue('menu');
}

However after saving it and opening it again I receive this error

InvalidArgumentException: The #default_value property has to be an entity object or an array of entity object

How do I successfully save or retrieve the menu? Do I need to put something like $this->configuration['menu']['value']?

Update: When I perform

die(print_r($this->configuration['menu']));

It just prints the machine name of the menu I selected. So maybe the issue is that the default value it's being supplied is just a string instead of the actual entity? But if so how would I get the entity from the machine name?

Update 2: I tried using

$menu = Entity::load($this->configuration['menu']);
die(print_r($menu));

But that didn't produce anything.

Answer 1

I was able to resolve the issue by loading the entity first like so

$menu = \Drupal::entityTypeManager()->getStorage('menu')->load($this->configuration['menu']);
    $form['menu'] = [
    '#type'          => 'entity_autocomplete',
    '#target_type'   => 'menu',
    '#default_value' => $menu,
];

The value of $this->configuration['menu'] was only the machine name, not the actual entity. So the entity had to be loaded and stored in a variable first.