原则 2：如何在 trait 中动态解析“targetEntity”和 JoinTable“name”？

Question

I want to create Entity which will implement following interface.

<?php

namespace App\Entity\Interfaces;
#...

interface FooInterface
{
    /**
     * @param ArrayCollection|FooInterface[] $foo
     */
    public function setFoo($foo);

    /**
     * @return ArrayCollection|FooInterface[]
     */
    public function getFoo();
}

To make it simple I want to use trait to inherit properties and methods from it. So finally my entities could look similar to these:

<?php

namespace App\Entity\Entity;
#...

class Bar implements FooInterface
{
    use FooTrait;
}

and

<?php

namespace App\Entity\Entity;
#...

class Baz implements FooInterface
{
    use FooTrait;
}

But I don't know how to resolve targetEntity and name dynamically in @ORM annotation.

<?php

namespace App\Entity\Traits;
#...

trait FooTrait
{
    /**
     * Many Foo has Many Foo.
     *
     * @ORM\ManyToMany(targetEntity="...")
     * @ORM\JoinTable(
     *     name="..."
     *     joinColumns={@ORM\JoinColumn(name="foo_id", referencedColumnName="id")},
     *     inverseJoinColumns={@ORM\JoinColumn(name="foo_of_id", referencedColumnName="id")}
     * )
     * @ORM\OrderBy({"id" = "ASC"})
     *
     * @var FooInterface[]|ArrayCollection
     */
    protected $foo;

    #...
}

Is the approach I chose a good one? If so how I can resolve my issue?

Answer 1

I've done this before, it's pretty fun and a bit complex, but gives your application tons of flexibility. What you are trying to do is called Dynamic Relationship Mapping.

The detailed tutorial is here . I'll recommend you take a look at it. I'll just summarize the steps here:

1. First you need to empty the fields of ORM Annotations of the relationships you want to dynamically map. You cannot do this with annotations.

2. Second, you need to create an event subscriber/listener, listening for the loadClassMetadata event.

3. Then you need to listen just for the entities that implement the desired interface. You will receive an instance of ClassMetadata on the event, that contains the ReflectionClass of your entity in-memory and a bunch of useful methods to check if implements a given interface or not, and so on, eg:

   $metadata = $eventArgs->getMetadata();
   if (!array_key_exists(FooInterface::class,
       $metadata->getReflectionClass()->getInterfaces())) {
            return;
   }

4. Depending of your needs, you have to call either $metadata->mapManyToMany() , ->mapManyToOne() , ->mapOneToMany() etc. It takes as argument a complex and well defined array, that contains almost the same info you will put in an annotation. You can leave most of them empty to use the default. What is required is that you provide the targetEntity and the fieldName (ie, the name of the property in your entity class).

5. Save it and register your listener as a service. You can debug your array configuration of step 4 with the doctrine console command orm:schema-tool:update --dump-sql , which prints out the SQL queries it would generate.

SIDE NOTE: This is not an expensive operation because the classMetadata is cached by doctrine.