Why didn't the key of the related table populate?

Question

Laravel

migration

Schema::create('companies', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->foreignIdFor(CompanyForm::class);

the code

$company = new Company();
$company->form()->firstOrCreate(
               // данные. Создается успешно.
            )
// code

$company->save();

$company->form()

public function form()
    {
        return $this->belongsTo(CompanyForm::class);
    }

Mistake

ERROR: null value in column "company_form_id" violates not-null constraint

Shouldn't company_form_id be automatically substituted?

Answer 1

Try to print what comes out in the form without creating.
This can be done in Laravel replay

php artisan tinker
>>> $u  = User::first()
[!] Aliasing 'User' to 'App\User' for this Tinker session.
=> App\User {#4365
     id: "1",
     name: "Sandrine Cormier",
     email: "[email protected]",
     email_verified_at: "2020-10-07 16:19:15",
     created_at: "2020-10-07 16:19:15",
     updated_at: "2020-10-07 16:19:15",
     deleted_at: null,
   }
>>> $u->completedExercises()->make([])
=> App\CompletedExercise {#4350
     user_id: 1,
   }
>>>

Answer 2

1. create, update call save themselves.
2. Even to think logically, then the relationship is called to an empty object of the newly created model, where does it get this ID from ?.
3. Forget about new to models. With this, all the magic disappears.
In general, to be honest, this code shows that you need to read the documentation. It's all there with examples.