Add Auth::user() to Eloquent save (); request - laravel-5.3

Question

How can I write the two lines of code below into one line of code:
$service_review->user_id=\Auth::user();
$user_service->service_reviews()->save($service_review);
The reason being that the line including Auth::user() is throwing an error since it's a foreign key in my "service_reviews" table and so "DOESN'T HAVE A DEFAULT VALUE"
The problem is if I give precedence to:
\Auth::user()->service_reviews()->save($service_review);
Then in this case, the authorized user is fetched but my user_service_id now throws the error as "DOESN'T HAVE A DEFAULT VALUE".
The code of my store method (This is from my ReviewsController that is based on a Nested Route:
Route::resource("services.reviews", "ReviewsController"); is as follows:
public function store(ReviewsRequest $request, $id){
$service_review = new Service_review($request->all());
$user_service = User_service::findOrFail($id);
$service_review->user_id=\Auth::user();
$user_service->service_reviews()->save($service_review);
return redirect("reviews");
I reckon passing them in one line of code will solve this error.

Answer 1

Yes your're right #MinaAbadir
I ended up doing it as follows:
public function store(ReviewsRequest $request, $id){
$service_review = new Service_review($request->all());
$user_service = User_service::findOrFail($id);
$service_review->user_id = \Auth::user()->email;
$user_service->service_reviews()->save($service_review);
return redirect("reviews");
}
It seems calling the specific column you want retrieved negates the foreign key problem. Maybe MySQL figures out the relationship via Eloquent. Let me know if I can clean this up further.