schmunk42\giiant\generators\crud\providers\core\RelationProvider::activeField PHP Method

    public function activeField($attribute)
    {
        $column = $this->generator->getColumnByAttribute($attribute);
        if (!$column) {
            return;
        }
        $relation = $this->generator->getRelationByColumn($this->generator->modelClass, $column);
        if ($relation) {
            switch (true) {
                case !$relation->multiple:
                    $pk = key($relation->link);
                    $name = $this->generator->getModelNameAttribute($relation->modelClass);
                    $method = __METHOD__;
                    switch ($this->inputWidget) {
                        case 'select2':
                            $code = <<<EOS
// generated by {$method}
\$form->field(\$model, '{$column->name}')->widget(\\kartik\\select2\\Select2::classname(), [
    'name' => 'class_name',
    'model' => \$model,
    'attribute' => '{$column->name}',
    'data' => \\yii\\helpers\\ArrayHelper::map({$relation->modelClass}::find()->all(), '{$pk}', '{$name}'),
    'options' => [
        'placeholder' => {$this->generator->generateString('Type to autocomplete')},
        'multiple' => false,
        'disabled' => (isset(\$relAttributes) && isset(\$relAttributes['{$column->name}'])),
    ]
]);
EOS;
                            break;
                        default:
                            $code = <<<EOS
// generated by {$method}
\$form->field(\$model, '{$column->name}')->dropDownList(
    \\yii\\helpers\\ArrayHelper::map({$relation->modelClass}::find()->all(), '{$pk}', '{$name}'),
    [
        'prompt' => {$this->generator->generateString('Select')},
        'disabled' => (isset(\$relAttributes) && isset(\$relAttributes['{$column->name}'])),
    ]
);
EOS;
                            break;
                    }
                    return $code;
                default:
                    return;
            }
        }
    }

 public function activeField($column)
 {
     return TabPadding::pad(parent::activeField($column));
 }