如何添加依赖于另一个的选择下拉列表？

Question

I've a form with 2 dropdown lists. The first one with molecule families and the second with molecule subgroup. When someone choose a family, he should only see the subgroups related to this family in the second dropdown.

My Form Type:

public function buildForm(FormBuilderInterface $builder, array $options)
{
    $builder
        ->add('Families', ChoiceType::class, array(
            'choices' => array(
                'Monosaccharides' => 'Monosaccharides',
                'Oligosaccharides ' => 'Oligosaccharides ',
                'Polysaccharides' => 'Polysaccharides'
            ),
            'placeholder' => 'Choose an option',
            'required' => false
        ))
        ->add('MolecularGroups', ChoiceType::class, array(
            'choices' => array(
                'Monosaccharide' => 'Monosaccharide',
                'Oligosaccharide' => 'Oligosaccharide',
                'Cyanogenic glycoside' => 'Cyanogenic glycoside'
            ),
            'placeholder' => 'Choose an option',
            'required' => false
        ));
}

Can someone show me the Symfony documentation about how to implement that?

Answer 1

The Question:

Can someone show me a documentation on how to do that?

The Documentation references:

• How to Dynamically Modify Forms Using Form Events
• Form Events