First steps using the ODM

Creating a Document Class

Suppose you're building an application where products need to be displayed. Without even thinking about Doctrine or MongoDB, you already know that you need a Product object to represent those products. Create this class inside the Document directory of your AcmeStoreBundle:

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// src/Acme/StoreBundle/Document/Product.php
namespace Acme\StoreBundle\Document;

class Product
{
    protected $name;

    protected $price;
}
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The class - often called a document, meaning a basic class that holds data - is simple and helps fulfill the business requirement of needing products in your application. This class can't be persisted to Doctrine MongoDB yet - it's just a simple PHP class.

Add Mapping Information

Doctrine allows you to work with MongoDB in a much more interesting way than just fetching data back and forth as an array. Instead, Doctrine allows you to persist entire objects to MongoDB and fetch entire objects out of MongoDB. This works by mapping a PHP class and its properties to entries of a MongoDB collection.

For Doctrine to be able to do this, you just have to create metadata, or configuration that tells Doctrine exactly how the Product class and its properties should be mapped to MongoDB. This metadata can be specified in a number of different formats including XML or directly inside the Product class via annotations:

Persisting Objects to MongoDB

Now that you have a mapped Product document complete with getter and setter methods, you're ready to persist data to MongoDB. From inside a controller, this is pretty easy. Add the following method to the DefaultController of the bundle:

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// src/Acme/StoreBundle/Controller/DefaultController.php
use Acme\StoreBundle\Document\Product;
use Doctrine\ODM\MongoDB\DocumentManager;
use Symfony\Component\HttpFoundation\Response;
// ...

public function createAction(DocumentManager $dm)
{
    $product = new Product();
    $product->setName('A Foo Bar');
    $product->setPrice('19.99');

    $dm->persist($product);
    $dm->flush();

    return new Response('Created product id '.$product->getId());
}
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Let's walk through this example:

• lines 8-10 In this section, you instantiate and work with the $product object like any other, normal PHP object;
• line 12 This line fetches Doctrine's document manager object, which is responsible for handling the process of persisting and fetching objects to and from MongoDB;
• line 13 The persist() method tells Doctrine to "manage" the $product object. This does not actually cause a query to be made to MongoDB (yet);
• line 14 When the flush() method is called, Doctrine looks through all of the objects that it's managing to see if they need to be persisted to MongoDB. In this example, the $product object has not been persisted yet, so the document manager makes a query to MongoDB, which adds a new entry.

If you are using `autowiring`, you can use type hinting to fetch the doctrine_mongodb.odm.document_manager service:

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// App/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Doctrine\ODM\MongoDB\DocumentManager as DocumentManager;
use App\Document\Product;
use Symfony\Component\HttpFoundation\Response;

class DefaultController extends AbstractController
{
    public function createProduct(DocumentManager $dm)
    {
        $product = new Product();
        $product->setName('A Foo Bar');
        $product->setPrice('19.99');

        $dm->persist($product);
        $dm->flush();

        return new Response('Created product id '.$product->getId());
    }
}
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When creating or updating objects, the workflow is always the same. In the next section, you'll see how Doctrine is smart enough to update entries if they already exist in MongoDB.

Fetching Objects from MongoDB

Fetching an object back out of MongoDB is even easier. For example, suppose you've configured a route to display a specific Product based on its id value:

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public function showAction(DocumentManager $dm, $id)
{
    $product = $dm->getRepository(Product::class)->find($id);

    if (!$product) {
        throw $this->createNotFoundException('No product found for id '.$id);
    }

    // do something, like pass the $product object into a template
}
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When you query for a particular type of object, you always use what's known as its repository. You can think of a repository as a PHP class whose only job is to help you fetch objects of a certain class. You can access the repository object for a document class via:

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$repository = $dm->getRepository(Product::class);

Once you have your repository, you have access to all sorts of helpful methods:

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// query by the identifier (usually "id")
$product = $repository->find($id);

// dynamic method names to find based on a column value
$product = $repository->findOneById($id);
$product = $repository->findOneByName('foo');

// find *all* products
$products = $repository->findAll();

// find a group of products based on an arbitrary column value
$products = $repository->findByPrice(19.99);
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You can also take advantage of the useful findBy() and findOneBy() methods to easily fetch objects based on multiple conditions:

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// query for one product matching be name and price
$product = $repository->findOneBy(array('name' => 'foo', 'price' => 19.99));

// query for all products matching the name, ordered by price
$product = $repository->findBy(
    array('name' => 'foo'),
    array('price' => 'ASC'),
);
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Updating an Object

Once you've fetched an object from Doctrine, updating it is easy. Suppose you have a route that maps a product id to an update action in a controller:

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public function updateAction(DocumentManager $dm, $id)
{
    $product = $dm->getRepository(Product::class)->find($id);

    if (!$product) {
        throw $this->createNotFoundException('No product found for id '.$id);
    }

    $product->setName('New product name!');
    $dm->flush();

    return $this->redirectToRoute('homepage');
}
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Updating an object involves just three steps:

1. Fetching the object from Doctrine;
2. Modifying the object;
3. Calling flush() on the document manager.

Notice that calling $dm->persist($product) isn't necessary. Recall that this method simply tells Doctrine to manage or watch the $product object. In this case, since you fetched the $product object from Doctrine, it's already managed.

Deleting an Object

Deleting an object is very similar, but requires a call to the remove() method of the document manager:

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$dm->remove($product);
$dm->flush();
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As you might expect, the remove() method notifies Doctrine that you'd like to remove the given document from the MongoDB. The actual delete operation however, isn't actually executed until the flush() method is called.