当用户使用post方法完成订单时，我试图通过从数据库中的产品数量中减去购物车项目数量来更新我的库存水平。每次运行该方法时，success函数都会出现，但字段不会更新。
有人能告诉我为什么吗？
我的控制器：

public function index ()
{
    $products = Product::all();

    return view('products', compact('products'));
}

public function cart()

{
    return view('cart');
}

public function addToCart($id)
{
    $product = Product::find($id);

    if(!$product) {

        abort(404);

    }

    $cart = session()->get('cart');

    // if cart is empty then this will be the first product
    if(!$cart) {

        $cart = [
                $id => [
                    "name" => $product->name,
                    "quantity" => 1,
                    "price" => $product->unit_price
                ]
        ];

        session()->put('cart', $cart);

        return redirect()->back()->with('success', 'Product added to cart successfully!');
    }

    // if cart isnt empty then check if this product exist then increment quantity
    if(isset($cart[$id])) {

        $cart[$id]['quantity']++;

        session()->put('cart', $cart);

        return redirect()->back()->with('success', 'Product added to cart successfully!');

    }

    // if item doesnt exist in cart then add to cart with quantity = 1
    $cart[$id] = [
        "name" => $product->name,
        "quantity" => 1,
        "price" => $product->unit_price
    ];

    session()->put('cart', $cart);

    return redirect()->back()->with('success', 'Product added to cart successfully!');
}

public function update(Request $request)
{
    if($request->id and $request->quantity)
    {
        $cart = session()->get('cart');

        $cart[$request->id]["quantity"] = $request->quantity;

        session()->put('cart', $cart);

        session()->flash('success', 'Cart updated successfully');
    }
}

public function remove(Request $request)
{
    if($request->id) {

        $cart = session()->get('cart');

        if(isset($cart[$request->id])) {

            unset($cart[$request->id]);

            session()->put('cart', $cart);
        }

        session()->flash('success', 'Product removed successfully');
    }
}

public function stock (Request $request)
{
    if($request->id and $request->quantity)
    {
        $cart = session()->get('cart');

        $cart[$request->id]['quantity'] = $request->quantity;

        $products = Product::all();

        $stock = $products->unit_stock;

        $quantity = $stock - $cart;

        return $quantity;
    }
}

我的路线：

Route::post('stock', 'ProductController@stock');

我的视图cart.blade.php：

@extends('layout')

@section('content')

<table id="cart" class="table table-hover table-condensed">
    <thead>
    <tr>
        <th style="width:50%">Product</th>
        <th style="width:10%">Price</th>
        <th style="width:8%">Quantity</th>
        <th style="width:22%" class="text-center">Subtotal</th>
        <th style="width:10%"></th>
    </tr>
    </thead>
    <tbody>

    <?php $total = 0 ?>

    @if(session('cart'))
        @foreach(session('cart') as $id => $details)

            <?php $total += $details['price'] * $details['quantity'] ?>

            <tr>
                <td data-th="Product">
                    <div class="row">

                        <div class="col-sm-9">
                            <h4 class="nomargin">{{ $details['name'] }}</h4>
                        </div>
                    </div>
                </td>
                <td data-th="Price">${{ $details['price'] }}</td>
                <td data-th="Quantity">
                    <input type="number" value="{{ $details['quantity'] }}" class="form-control quantity" />
                </td>
                <td data-th="Subtotal" class="text-center">${{ $details['price'] * $details['quantity'] }}</td>
                <td class="actions" data-th="">
                    <button class="btn btn-info btn-sm update-cart" data-id="{{ $id }}"><i class="fa fa-refresh"></i></button>
                    <button class="btn btn-danger btn-sm remove-from-cart" data-id="{{ $id }}"><i class="fa fa-trash-o"></i></button>
                </td>
            </tr>
        @endforeach
    @endif

    </tbody>
    <tfoot>
    <tr class="visible-xs">
        <td class="text-center"><strong>Total {{ $total }}</strong></td>
    </tr>
    <tr>
        <td><a href="{{ url('/products') }}" class="btn btn-warning"><i class="fa fa-angle-left"></i> Continue Shopping</a></td>
        <td colspan="2" class="hidden-xs"></td>
        <td class="hidden-xs text-center"><strong>Total ${{ $total }}</strong></td>
    </tr>
    </tfoot>

    <div class="row">
       <div class="btn col-md-12">
           <a href="{{ url('/cart') }}" id="order-complete">Test</a>
       </div>

    </div>
</table>

<script type="text/javascript">

    $("#order-complete").click(function (e){
       e.preventDefault();

        var ele = $(this);

        $.ajax({
           url: '{{ url('stock') }}',
           method: "post",
           data: {_token: '{{ csrf_token() }}'},
           success: function () {

            window.location.reload();
           }
        });
    });
</script>

@endsection