class Mapping

1. 8.x drupal/core/lib/Drupal/Core/Config/Schema/Mapping.php \Drupal\Core\Config\Schema\Mapping
2. 8.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/style/Mapping.php \Drupal\views\Plugin\views\style\Mapping

picture.schema.yml in drupal/core/modules/picture/config/schema/picture.schema.yml

drupal/core/modules/picture/config/schema/picture.schema.yml

system.data_types.schema.yml in drupal/core/modules/system/config/schema/system.data_types.schema.yml

drupal/core/modules/system/config/schema/system.data_types.schema.yml

system.data_types.schema.yml in drupal/core/modules/system/config/schema/system.data_types.schema.yml

drupal/core/modules/system/config/schema/system.data_types.schema.yml

class Mapping extends ArrayElement implements ComplexDataInterface {

  /**
   * Overrides ArrayElement::parse()
   */
  protected function parse() {
    $elements = array();
    foreach ($this->definition['mapping'] as $key => $definition) {
      if (isset($this->value[$key])) {
        $elements[$key] = $this
          ->parseElement($key, $this->value[$key], $definition);
      }
    }
    return $elements;
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::get().
   */
  public function get($property_name) {
    $elements = $this
      ->getElements();
    if (isset($elements[$property_name])) {
      return $elements[$property_name];
    }
    else {
      throw new InvalidArgumentException(format_string("The configuration property @key doesn't exist.", array(
        '@key' => $property_name,
      )));
    }
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::set().
   */
  public function set($property_name, $value, $notify = TRUE) {

    // Notify the parent of any changes to be made.
    if ($notify && isset($this->parent)) {
      $this->parent
        ->onChange($this->name);
    }

    // Set the data into the configuration array but behave according to the
    // interface specification when we've got a null value.
    if (isset($value)) {
      $this->value[$property_name] = $value;
      return $this
        ->get($property_name);
    }
    else {

      // In these objects, when clearing the value, the property is gone.
      // As this needs to return a property, we get it before we delete it.
      $property = $this
        ->get($property_name);
      unset($this->value[$property_name]);
      $property
        ->setValue($value);
      return $property;
    }
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::getProperties().
   */
  public function getProperties($include_computed = FALSE) {
    return $this
      ->getElements();
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::getPropertyValues().
   */
  public function getPropertyValues() {
    return $this
      ->getValue();
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::setPropertyValues().
   */
  public function setPropertyValues($values) {
    foreach ($values as $name => $value) {
      $this->value[$name] = $value;
    }
    return $this;
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinition().
   */
  public function getPropertyDefinition($name) {
    if (isset($this->definition['mapping'][$name])) {
      return $this->definition['mapping'][$name];
    }
    else {
      return FALSE;
    }
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
   */
  public function getPropertyDefinitions() {
    $list = array();
    foreach ($this
      ->getAllKeys() as $key) {
      $list[$key] = $this
        ->getPropertyDefinition($key);
    }
    return $list;
  }

  /**
   * Implements Drupal\Core\TypedData\ComplexDataInterface::isEmpty().
   */
  public function isEmpty() {
    return empty($this->value);
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::onChange().
   */
  public function onChange($property_name) {

    // Notify the parent of changes.
    if (isset($this->parent)) {
      $this->parent
        ->onChange($this->name);
    }
  }

}