Call to a member function save() on a non-object

I am building a small laravel app beginning level. I got error in code in I couldn't solve out. Here is the code

post model

namespace App;

use Illuminate\Database\Eloquent\Model;

class post extends Model
{
    public function user()
    {
      return $this->belongsTo('app\user');
    }
}

user model

namespace App;

use Illuminate\Contracts\Auth\Authenticatable;
use Illuminate\Database\Eloquent\Model;


class user extends Model implements Authenticatable
{
  use \Illuminate\Auth\Authenticatable;
  public function posts()
  {
    $this->hasMany('app\post');
  }
}

postcontroller

namespace App\Http\Controllers;
use App\post;
use Illuminate\Http\Request;

class postcontroller extends Controller{
  public function postCreatePost(Request $request){
    $post = new post();
    $post->body = $request['body'];
    $request->user()->posts()->save($post);
    return redirect()->route('dashboard');
  }
}

Thank you in advance for any try from you to solve this query.

via Chebli Mohamed