Laravel 5.4 how to properly inject a dependency into a POST request?

Question

Laravel

For example, I have a form, it has a user_name field, I would not want to write this in the controller:

public function postDoSomething(Request $request)
{
    //code...
    $user = User::where('name', '=', $request->user_name)->first();
    //code...
}

How can you inject a dependency in such a case that an already found user comes to the request?

Answer 1

Route Model Binding

Answer 2

There is an example in the doc.