Symfony 5：在属性路径“myEntity”中给出的“字符串”、“对象”类型的预期参数

Question

I am having an issue with the EntityType class in Symfony 5 where I cannot find a way to make the form row return a string instead of an entity ( MyEntity ). This is what I basically have as part of the form builder:

$builder->add('myEntity', EntityType::class, [
                'class' => MyEntity::class,
                'placeholder' => "(Please select an option.)",
                'choice_label' => 'name'
            ])

My aim is to have this field return the name for the MyEntity selected, not the entire entity (so, the exact same value as the 'choice_label' ). I've already tried adding a 'choice_value' => 'name' attribute (with a 'mapped' => false attribute, which is apparently necessary in that case), but to no avail. More precisely, the form row starts returning null rather than a string for any entity.

How would I be able to achieve my goal?

Answer 1

It turns out that defining the __toString() function in MyEntity as returning the name field (the exact same way you would define getName() ) fixed it, and I now get no errors plus a successful submission to the DB.

public function __toString() {
    return $this->name;
}

(In case you're wondering why just this addition and nothing else fixes it, it's because __toString is already being used by default in some pre-existing entity-related code to express an entity in a simpler and custom way, if I'm not mistaken. Now that I made this function available, it's going to go to it and safely assume that when my entity might need to be expressed in a simpler [string] format, __toString should be called to "transform" MyEntity into a meaningful string, such as its name . I guess all that is to say that for instance, you won't refer to a car by all of its internal parts, but rather by just its model.)

Answer 2

I'm glad you found the right solution, but it didn't work for me. I use the EntityType in its own Type which is called in a CollectionType (yes, something special). To solve the problem for me, I used the DataTransformer, as follows:

class ProductTextTransformer implements DataTransformerInterface
{

  public function reverseTransform($text)
  {
      if (null === $text) {
          return '';
      }

      return $text->getName();
  }

  public function transform($name)
  {
      // NOTE: Should not Called!
  }
}