Laravel BelongsTo relation - where on instance attribute - laravel

Question

I have the following model:
class Order extends Model
{
public function user(): BelongsTo
{
return $this->belongsTo(User::class, 'shipping_email_address', 'email_address')
->where('customer_id', $this->customer_id);
}
}
Now when I call Order::with('user')->get(), it doesn't load the users.
I can access the user just fine when using Order::first()->user.
Is it possible to eager load a relationship with a where clause on a model instance attribute (like $this->customer_id)? Or is there another way to make a relationship based on two columns?

Answer 1

You can do this :
Your relation :
public function user()
{
return $this->belongsTo(User::class);
}
Then you can make query like this :
$userId = 5;
$result = Order::whereHas('user',function($q) use ($userId){
return $q->where('id',$userId);
});
Reply to your comment:
Having this relation :
public function user()
{
return $this->belongsTo(User::class);
}
Use this :
Order::with('user')->get()
This will retrieve all orders with its users. If you have some problem on that query then you have a wrong relationship. Make sure you have a foregin key in Orders table, if you dont espcify some foreign key on eloquent relationship, eloquent will understand than foreign key is : user_id, if not, especify putting more arguments to this function :
$this->belongsTo(User::class,...,...);
With function make join according to relationship configuration, just make sure the relation is ok. And all work fine !

Answer 2

If you want to keep your current flow, i would do it like so. Thou the josanangel solution is most optimal.
When getting orders include them using with. All these are now eager loaded.
$orders = Order::with('user');
Now utilize eloquent getters to filter the user by customer_id. This is not done in queries, as that would produce one query per attribute access.
public function getUserByCustomerAttribute() {
if ($this->user->customer_id === $this->customer_id) {
return $this->user;
}
return null;
}
Simply accessing the eloquent getter, would trigger your custom logic and make what you are trying to do possible.
$orders = Order::with('user')->get();
foreach ($orders as $order) {
$order->user_by_customer; // return user if customer id is same
}

Answer 3

Your wrong decleration of the relationship here is what is making this not function correctly.
From the laravel's documentation:
Eloquent determines the default foreign key name by examining the name of the relationship method and suffixing the method name with a _ followed by the name of the parent model's primary key column. So, in this example, Eloquent will assume the Post model's foreign key on the comments table is post_id.
in your case the problem is that laravel is searching for the User using user_id column so the correct way to declare the relation is
public function user()
{
return $this->belongsTo(User::class, 'customer_id'); // tell laravel to search the user using this column in the Order's table.
}
Everthing should work as intended after that.
Source: documentation