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04.

JoinColumn & Relations in Fixtures

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Is the relationship required in the database? I mean, could I save a GenusNote without setting a Genus on it? Actually, I could! Unlike a normal column, relationship columns - for whatever reason - are optional by default. But does it make sense to allow a GenusNote without a Genus? No! That's crazy talk! Let's prevent it.

Find the ManyToOne annotation and add a new annotation below it: JoinColumn. Inside, set nullable=false:

101 lines | src/AppBundle/Entity/GenusNote.php
// ... lines 1 - 10
class GenusNote
{
// ... lines 13 - 39
/**
* @ORM\ManyToOne(targetEntity="Genus")
* @ORM\JoinColumn(nullable=false)
*/
private $genus;
// ... lines 45 - 99
}

The JoinColumn annotation controls how the foreign key looks in the database. And obviously, it's optional. Another option is onDelete: that literally changes the ON DELETE behavior in your database - the default is RESTRICT, but you can also use CASCADE or SET NULL.

Anyways, we just made a schema change - so time to generate a migration!

./bin/console doctrine:migrations:diff

This time, I'll be lazy and trust that it's correct. Run it!

./bin/console doctrine:migrations:migrate

When Migrations Go Wrong

Ah, it explodes! Null value not allowed? Why? Think about what's happening: we have a bunch of existing GenusNote rows in the database, and each still has a null genus_id. We can't set that column to NOT NULL because of the data that's already in the database.

If the app were already deployed to production, we would need to fix the migration: maybe UPDATE each existing genus_note and set the genus_id to the first genus in the table.

But, alas! We haven't deployed to production yet: so there isn't any existing production database that we'll need to migrate. Instead, just start from scratch: drop the database completely, re-create it, and re-migrate from the beginning:

./bin/console doctrine:database:drop --force

./bin/console doctrine:database:create

./bin/console doctrine:migrations:migrate

Phew! Now it works great.

Tip

If you still get an error while running the migration, it's because of a MySQL change! Find the details here: http://bit.ly/migrations-tweak

Relations in Fixtures

Last step! Our fixtures are broken: we need to associate each GenusNote with a Genus. We know how to set normal properties, like username and userAvatarFilename. But how can we set relations? As usual with Alice: it's so nice. Use genus: @ then the internal name of one of the 10 genuses - like genus_1. That's it!

But, you know what? That's not awesome enough. I really want this to be a random Genus. Ok: change that genus_1 to genus_*:

16 lines | src/AppBundle/DataFixtures/ORM/fixtures.yml
// ... lines 1 - 8
AppBundle\Entity\GenusNote:
genus.note_{1..100}:
// ... lines 11 - 14
genus: '@genus_*'

Alice will now look at the 10 Genus objects matching this pattern and select a random one each time.

Reload the fixtures:

./bin/console doctrine:fixtures:load

It's alive! Check out the results again with doctrine:query:sql:

./bin/console doctrine:query:sql 'SELECT * FROM genus_note'

Every single one has a random genus. Do you love it? I love it.