class FloatItem

class FloatItem extends NumericItemBase {
  
  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
    $properties['value'] = DataDefinition::create('float')->setLabel(t('Float'))
      ->setRequired(TRUE);
    return $properties;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function schema(FieldStorageDefinitionInterface $field_definition) {
    return [
      'columns' => [
        'value' => [
          'type' => 'float',
        ],
      ],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function fieldSettingsForm(array $form, FormStateInterface $form_state) {
    $element = parent::fieldSettingsForm($form, $form_state);
    $element['min']['#step'] = 'any';
    $element['max']['#step'] = 'any';
    return $element;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
    $settings = $field_definition->getSettings();
    $precision = rand(10, 32);
    $scale = rand(0, 2);
    $max = is_numeric($settings['max']) ? $settings['max'] : pow(10, $precision - $scale) - 1;
    $min = is_numeric($settings['min']) ? $settings['min'] : -pow(10, $precision - $scale) + 1;
    // @see "Example #1 Calculate a random floating-point number" in
    // http://php.net/manual/function.mt-getrandmax.php
    $random_decimal = $min + mt_rand() / mt_getrandmax() * ($max - $min);
    $values['value'] = self::truncateDecimal($random_decimal, $scale);
    return $values;
  }

}