binding models on request data in laravel

BookController.php

<?php namespace LS\Http\Controllers;

...

class AnnualReportController extends Controller
{
    public function store(BookRequest $request, Book $newBook, Author $byAuthor)
    {
        $newBook->fill($request->all());
        $newBook->author()->associate($byAuthor);
        $newBook->save();

        return redirect('/book')->with('success', 'book has been succesfully created');
    }

RequestServiceProvider.php

<?php
namespace LS\Providers;

use Illuminate\Support\ServiceProvider;
use Illuminate\Support\Facades\Input;

class RequestServiceProvider extends ServiceProvider
{
    public function register()
    {
        /**
         * In this example, when the POST data contains author_id, 
         * the correct author model will be available from the service container.
         * This will work similar to route model binding.
         */
        $this->model('author_id', \Author::class);
    }

    /**
     * Bind models based on a key in the request data
     *
     * @param string $key
     * @param string $className
     */
    private function model($key, $className)
    {
        if (Input::has($key)) {

            $this->app->bind($className, function () use ($key, $className) {

                return $className::findOrFail(Input::get($key));
            });
        }
    }
}