Can someone explain how Laravel relationships work? - php

Question

When I save a post it saves id of user which posted it.
That is great but I don't understand how.
Post controller
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Post;
class PostController extends Controller
{
public function postCreatePost(Request $request)
{
$post = new Post();
$post->body = $request['body'];
$request->user()->posts()->save($post); //i cant understand this line
return redirect()->route('dashboard');
}
}
?>
User model
<?php
namespace App;
use Illuminate\Contracts\Auth\Authenticatable;
use Illuminate\Database\Eloquent\Model;
class User extends Model implements Authenticatable
{
use \Illuminate\Auth\Authenticatable;
public function posts()
{
return $this->hasMany('App\Post'); // ?
}
}
Post model
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Post extends Model
{
public function user()
{
return $this->belongsTo('App\User'); // ?
}
}
I don't understand how belongs to and has many relations work.
If someone could explain it to me I would be very grateful.

Answer 1

In this case, the hasMany indicates that it will find many rows with the user id on the user_id column in the posts table.
The belongsTo simply means that it will find a user with an id in the users table that matches the user_id column on the posts related row.
Finally, $request->user()->posts()->save($post);:
Get the request
Get the user from the request
Get the posts from the user
The ->save($model) is a bit tricker. This requires that the object passed to the ->save($object) function is an instance of the relationship. In our case, the relationship is posts() and therefore the $post simply has to be an instance of App\Post (or wherever your Models namespace is).

Answer 2

You can find an explanation in the official documentation and in the chapter "Eloquent Relationships" from the book "Code Smart" (Laravel 4).
You can find a lot more resources in Google.