Hey friends! I mean, hello fellow space-traveling developer... friends. Welcome, to part two of our Doctrine tutorial where we talk all about... relationships. Oh, I love relationships, and there are so many beautiful types in the universe! Like, the relationship between two old friends, as they high-five after a grueling trip between solar systems. Or, the complex relationship between a planet and a moon: a perfect gravitational dance between BFF's. And of course, the most incredible type of relationship in all of the galaxy... database relationships.
Sure, we learned a ton about Doctrine in the first tutorial, but we completely avoided this topic! And it turns out, database relationships are pretty darn important if you want to build one of those "real" applications. So let's crush them.
As always, to have the best possible relationship with Doctrine, you should totally
code along with me. Download the course code from this page. After you unzip the file,
you'll you'll find a
start/ directory that will have the same code you see here.
Check out the
README.md file for setup instructions, and the answer to this
KnpU space riddle:
My name sounds white & fluffy, but I'm not! And instead of blocking the sun, I orbit it.
Need to know the answer? Then download the course code! Anyways, the last setup step will be to open a terminal, move into the project directory and run:
php bin/console server:run
to start the built-in web server. Then, celebrate by finding your browser, and
http://localhost:8000. Hello: The Space Bar! Our hot new app that helps
spread real news to curious astronauts across the galaxy.
And thanks to the last tutorial, these articles are being loaded dynamically from the database. But... these comments at the bottom? Yea, those are still hardcoded. We need to fix that! And this will be our first relationship: each Article can have many Comments. But, more about that later.
src/Entity directory, the only entity we have so far is
before we can talk about relationships, we first need to build a
entity. We could create this by hand, but the generator is so much nicer:
Open a new terminal tab and run:
php bin/console make:entity
Name the entity Comment. Then, for the fields, we need one for the author and one
for the actual comment. Add
authorName as a string field. And yea, someday,
we might have a
User table. And then, this could be a relationship to that table.
But for now, keep it as a simple string.
content as a
text field, and also say no to nullable. Hit enter one
more time to finish up.
Oh, but before we generate the migration, go open the new
Comment class. No
content and some getter & setter methods. At the
top of the class, let's add
That will give us
Now head back to your terminal and run:
php bin/console make:migration
When that finishes, go find the new file. We just want to make sure that this doesn't
contain any surprise. For example, if you're working on multiple branches, then
your database may be out-of-sync before you run
make:migration. If that happens,
the migration file would contain extra changes that you'll want to remove. In this
case, it looks great.
Go back to your terminal and, migrate!
php bin/console doctrine:migrations:migrate
Perfect! We have an
article table and now a
comment table. But, they are
not friends yet. Time to add a relation!