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How to Reduce Code Duplication with "inherit_data"

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How to Reduce Code Duplication with "inherit_data"ΒΆ

New in version 2.3: This inherit_data option was introduced in Symfony 2.3. Before, it was known as virtual.

The inherit_data form field option can be very useful when you have some duplicated fields in different entities. For example, imagine you have two entities, a Company and a Customer:

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// src/AppBundle/Entity/Company.php
namespace AppBundle\Entity;

class Company
{
    private $name;
    private $website;

    private $address;
    private $zipcode;
    private $city;
    private $country;
}

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// src/AppBundle/Entity/Customer.php
namespace AppBundle\Entity;

class Customer
{
    private $firstName;
    private $lastName;

    private $address;
    private $zipcode;
    private $city;
    private $country;
}

As you can see, each entity shares a few of the same fields: address, zipcode, city, country.

Start with building two forms for these entities, CompanyType and CustomerType:

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// src/AppBundle/Form/Type/CompanyType.php
namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;

class CompanyType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('name', 'text')
            ->add('website', 'text');
    }
}

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// src/AppBundle/Form/Type/CustomerType.php
namespace AppBundle\Form\Type;

use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\AbstractType;

class CustomerType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('firstName', 'text')
            ->add('lastName', 'text');
    }
}

Instead of including the duplicated fields address, zipcode, city and country in both of these forms, create a third form called LocationType for that:

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// src/AppBundle/Form/Type/LocationType.php
namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class LocationType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('address', 'textarea')
            ->add('zipcode', 'text')
            ->add('city', 'text')
            ->add('country', 'text');
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'inherit_data' => true
        ));
    }

    public function getName()
    {
        return 'location';
    }
}

The location form has an interesting option set, namely inherit_data. This option lets the form inherit its data from its parent form. If embedded in the company form, the fields of the location form will access the properties of the Company instance. If embedded in the customer form, the fields will access the properties of the Customer instance instead. Easy, eh?

Note

Instead of setting the inherit_data option inside LocationType, you can also (just like with any option) pass it in the third argument of $builder->add().

Finally, make this work by adding the location form to your two original forms:

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// src/AppBundle/Form/Type/CompanyType.php
public function buildForm(FormBuilderInterface $builder, array $options)
{
    // ...

    $builder->add('foo', new LocationType(), array(
        'data_class' => 'AppBundle\Entity\Company'
    ));
}

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// src/AppBundle/Form/Type/CustomerType.php
public function buildForm(FormBuilderInterface $builder, array $options)
{
    // ...

    $builder->add('bar', new LocationType(), array(
        'data_class' => 'AppBundle\Entity\Customer'
    ));
}

That's it! You have extracted duplicated field definitions to a separate location form that you can reuse wherever you need it.

Caution

Forms with the inherit_data option set cannot have *_SET_DATA event listeners.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.