每个任务只允许一个反馈[Laravel 5]

I'm trying to make a feedback system where a user can only give one feedback per 'task'-item. Currently one user can give as many feedbacks as he/she wants but ofcourse I want to limit this, seeing there is a rating behind it, ect..

Any help would be much appreciated!

Thanks

These are my models:

//Feedback
    public function user()
    {
        return $this->belongsTo('App\User');   
    }

    public function tnb()
    {
        return $this->belongsTo('App\Tnb');   
    }

//Tnb
    public function user()
    {
        return $this->belongsTo('App\User');
    }

    public function feedbacks() 
    {
        return $this->hasMany('App\Feedback');
    }

// User
    public function tnbs()
    {
        return $this->hasMany('App\Tnb');
    }

    public function feedbacks() 
    {   
        return $this->hasMany('App\Feedback');
    }

My database tabels:

Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('username')->unique();
            $table->string('email')->unique();
            $table->string('password', 60);
            $table->rememberToken();
            $table->timestamps();
        });

        Schema::create('tnb', function (Blueprint $table) {
            $table->increments('id');
            $table->string('type');
            $table->string('name');
            $table->integer('user_id')->unsigned();
            $table->foreign('user_id')->references('id')->on('users')->onCascade('update')->onDelete('cascade');
            $table->integer('group_id')->unsigned();
            $table->foreign('group_id')->references('id')->on('groups')->onCascade('update')->onDelete('cascade');
            $table->string('desc');
            $table->string('slug');
            $table->date('startdate');
            $table->time('starttime');
            $table->date('enddate');
            $table->time('endtime');
            $table->timestamps();
        });

        Schema::create('feedbacks', function (Blueprint $table) {
            $table->increments('id');
            $table->string('score');
            $table->string('feedback');
            $table->integer('user_id')->unsigned();
            $table->foreign('user_id')->references('id')->on('users')->onCascade('update')->onDelete('cascade');
            $table->integer('tnb_id')->unsigned();
            $table->foreign('tnb_id')->references('id')->on('tnb')->onCascade('update')->onDelete('cascade');
            $table->timestamps();
        });

I've been trying a couple things in my controller but until now I'm not getting anywhere:

public function store(Request $request, Group $group, Tnb $tnb)
{
    $user = auth()->user();

    $feedback = new Feedback(
        array(
            'score' => $request->get('score'),
            'feedback' => $request->get('feedback')
            ));

    $feedback->user()->associate($user);

    //dd($feedback->user()->whereId(Auth::user()->id)->count());

    $tnb->feedbacks()->save($feedback);

    \Flash::success('Your feedback has succesfully been sumbitted!');
    return redirect()->back();
}

Found the solution!

public function store(Request $request, Group $group, Tnb $tnb)
    {
        $user = auth()->user();

        $feedback = new Feedback(
            array(
                'score' => $request->get('score'),
                'feedback' => $request->get('feedback')
                ));

        $feedback->user()->associate($user);

        foreach($user->feedbacks as $feedback)
        {
            if ($tnb->user_id == $user->id)
            {
                \Flash::error('You may not give a feedback on your own tasks and bookings!');
                return redirect()->back();

                if($feedback->user_id == $user->id)
                {
                    \Flash::error('You have already posted a feedback!');
                    return redirect()->back();
                }
            }
        }


        $tnb->feedbacks()->save($feedback);

        \Flash::success('Your feedback has succesfully been sumbitted!');
        return redirect()->back();
    }