Handling Relations to Collections

Currently, API Platform Admin doesn’t handle to-many relations. The core library is being patched to document relations to collections through OWL.

Meanwhile, it is possible to manually configure API Platform to handle relations to collections.

We will create the admin for an API exposing Person and Book resources linked with a many-to-many relation between them (through the authors property).

This API can be created using the following PHP code:

<?php
// api/src/Entity/Person.php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\ORM\Mapping as ORM;

/**
 * @ApiResource
 * @ORM\Entity
 */
class Person
{
    /**
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue
     * @ORM\Id
     */
    public $id;

    /**
     * @ORM\Column
     */
    public $name;
}

<?php
// api/src/Entity/Book.php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Mapping as ORM;

/**
 * @ApiResource
 * @ORM\Entity
 */
class Book
{
    /**
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue
     * @ORM\Id
     */
    public $id;

    /**
     * @ORM\ManyToMany(targetEntity="Person")
     */
    public $authors;

    public function __construct()
    {
        $this->authors = new ArrayCollection();
    }
}

Let’s customize the components used for the authors property:

import React, { Component } from 'react';
import { ReferenceArrayField, SingleFieldList, ChipField, ReferenceArrayInput, SelectArrayInput } from 'react-admin';
import { AdminBuilder, hydraClient } from '@api-platform/admin';
import parseHydraDocumentation from 'api-doc-parser/lib/hydra/parseHydraDocumentation';

const entrypoint = 'https://demo.api-platform.com';

export default class extends Component {
  state = {api: null, resources: null};

  componentDidMount() {
    parseHydraDocumentation(entrypoint).then({api, resources} => {
        const books = r.find(r => 'books' === r.name);

        // Set the field in the list and the show views
        books.readableFields.find(f => 'authors' === f.name).fieldComponent =
          <ReferenceArrayField label="Authors" reference="people" source="authors" key="authors">
            <SingleFieldList>
              <ChipField source="name" key="name"/>
            </SingleFieldList>
          </ReferenceArrayField>
        ;

        // Set the input in the edit and create views
        books.writableFields.find(f => 'authors' === f.name).inputComponent =
          <ReferenceArrayInput label="Authors" reference="people" source="authors" key="authors">
            <SelectArrayInput optionText="name"/>
          </ReferenceArrayInput>
        ;

        this.setState({api, resources});
      }
    )
  }

  render() {
    if (null === this.state.api) return <div>Loading...</div>;

    return <AdminBuilder api={this.state.api} dataProvider={hydraClient({entrypoint: entrypoint, resources: this.state.resources})}/>
  }
}

The admin now properly handles this to-many relation!

# Using an Autocomplete Input for Relations

We’ll make one last improvement to our admin: transforming the relation selector we just created to use autocompletion.

Start by adding a “partial search” filter on the name property of the Book resource class.

# api/config/services.yaml
services:
    person.search_filter:
        parent: 'api_platform.doctrine.orm.search_filter'
        arguments: [ { name: 'partial' } ]
        # Uncomment only if you don't use autoconfiguration
        #tags: ['api_platform.filter']

<?php
// api/src/Entity/Person.php
// ...

/**
 * @ApiResource(attributes={"filters"={"person.search_filter"}})
 * @ORM\Entity
 */
class Person
{
    // ...
}

Then edit the configuration of API Platform Admin to pass a filterToQuery property to the ReferenceArrayInput component.

  componentDidMount() {

    // ...

    // Set the input in the edit and create views
    books.writableFields.find(f => 'authors' === f.name).inputComponent =
      <ReferenceArrayInput label="Authors" reference="people" source="authors" key="authors" filterToQuery={searchText => ({ name: searchText })}>
        <SelectArrayInput optionText="name"/>
      </ReferenceArrayInput>
    ;

    // ...
  }

The autocomplete field should now work properly!