Laravel eloquent relationships hasMany two foreign keys error - laravel

Question

I use Laravel 7.2 and I've 2 models:
User
public function orders()
{
if($this->hasRole("seller")) {
return $this->hasMany('App\Models\Order', 'seller_id', 'id');
} else if($this->hasRole("client")) {
return $this->hasMany('App\Models\Order', 'user_id', 'id');
}
}
Order
Migration:
Schema::create('orders', function (Blueprint $table) {
$table->id();
$table->boolean('status')->default(false);
$table->text('description')->nullable();
$table->unsignedBigInteger('user_id');
$table->foreign('user_id')
->references('id')
->on('users')
->onDelete('cascade');
$table->unsignedBigInteger('seller_id');
$table->foreign('seller_id')
->references('id')
->on('users')
->onDelete('cascade');
$table->timestamps();
$table->softDeletes();
});
Code:
public function user()
{
return $this->belongsTo('App\Models\User', 'user_id');
}
public function seller()
{
return $this->belongsTo('App\Models\User', 'seller_id');
}
Now in my case users has two roles seller or client. But when I try get user orders laravel return me error message:
Call to a member function addEagerConstraints() on null
Or when I try get custom order user or seller related data also return same error message.
Where I've any error or I've create relationships incorrectly?

Answer 1

This occurs because the condition in the relation here:
public function orders()
{
if($this->hasRole("seller")) {
return $this->hasMany('App\Models\Order', 'seller_id', 'id');
} else if($this->hasRole("client")) {
return $this->hasMany('App\Models\Order', 'user_id', 'id');
}
}
Imagine users who has neither roles 'seller' or 'client' then Null will be returned and that is exactly the issue.
I recommend you to split the method orders into two methods sellerOrders and clientOrders.