Load the value of an entity field type in another form

Question

I have created a custom field and I wish to load the value dynamically in another form in relation to the specific node entity the value belongs to. I understand that to get the value I have to use/know the field_name like this

$entity->get('field_name')->getValue();

What I want is to get the field_name set via content configurations with only the type of node and the field name as defined in the fieldItem Plugin

$field_definitions = \Drupal::service('entity_field.manager')->getFieldStorageDefinitions('node');

When I dump $field_definitions am able to see all the fields array with all the details but I can't get my node.field_name in relation to the fieldItem name defined in the specific field plugin, in my case field_custom_example

/**
 * Plugin implementation of the 'field_custom_example' field type.
 *
 * @FieldType(
 *   id = "field_custom_example",
 *   label = @Translation("Custom Example"),
 *   description = @Translation("Stores data for Custom Example Field"),
 *   default_widget = "custom_example_widget",
 *   default_formatter = "custome_example_formatter"
 * )
 */

that's where am stuck.

Answer 1

Use the method FieldDefinitionInterface::getType:

Returns the field type.

Return value

(string) The field type, i.e. the id of a field type plugin. For example 'text'.

In your case for example:

foreach ($field_definitions as $name => $definition) {
  if ($definition->getType() == 'field_custom_example') {
    // found field $name
  }
}