How to get all Fields of specific FieldType?

Question

What I'm trying to do is ->

 $fields = [];
  $fields = $entity->getFieldDefinitions();  
  foreach ($fields as $field) {
    if ($field->field_type == 'type') {
      $test = $field->field_type;
    }
  }

Unfortunately I couldn't find a neat method to select my fields by type, so I thought unless Drupal won't give me one I write my own. But Drupal restrict me on that also with this -> Fatal error: Cannot access protected property

Fatal error: Cannot access protected property Drupal\field\Entity\FieldConfig::$field_type

Answer 1

You code is OK, only that you are trying to read the protected property field_type. Instead use the method:

$field->getType()

Reference: public function FieldDefinitionInterface::getType()

Answer 2

Here is a quick rundown how I retrieved this information:

• Opened up FieldConfig (core/modules/field/src/Entity/FieldConfig.php)
• Searched for $field_type
• Nothing useful
• Went to the base class FieldConfigBase (core/lib/Drupal/Core/Field/FieldConfigBase.php)

• Search results:

  • First one: protected $field_type; (okay protected, as expected. This is why it doesn't work)

  • Second result public function getType() { return $this->field_type; }

    This seems to be what we want.

  • Let's see which interface defines this method: My IDE tells me: \Drupal\Core\Field\FieldDefinitionInterface::getType

For a little bit nicer code, here is a function which returns all field definitions (note: this are not the fields actually having the values) by field type:

function getFieldDefinitionsByType(FieldableEntityInterface $entity, $field_type) {
  $fields = $entity->getFieldDefinitions();
  $fields_by_type = array_filter($fields, function (FieldDefinitionInterface $field_definition) use ($field_type) {
    return $field_definition->getType() == $field_type;
  });
  return $fields_by_type;
}