Laravel 8 array_key_exists() 中的数组键错误答案

【问题标题】：Array key error in Laravel 8 array_key_exists()Laravel 8 array_key_exists() 中的数组键错误
【发布时间】：2021-09-22 03:21:56
【问题描述】：

我得到 array_key_exists() 期望参数 2 是数组，给定 null 在下面的代码中。我知道这是因为$this->items;为空，但我不确定如何修复它。

警告：array_key_exists() 期望参数 2 为数组，给定为空

public function __construct($cart = null)
{
    if ($cart) {
        $this->items = $cart->items;
        $this->totalPrice = $cart->totalPrice;
        $this->totalQty = $cart->totalQty;
    } else {
        $this->items = [];
        $this->totalQty = 0;
        $this->totalPrice = 0;
    }
}

public function add($product)
{
    $item = [
        'id' => $product->id,
        'name' => $product->name,
        'price' => $product->price,
        'qty' => 0,
        'image' => $product->image

    ];
    if (!array_key_exists($product->id, $this->items)) {
        $this->items[$product->id] = $item;
        $this->totalQty += 1;
        $this->totalPrice += $product->price;
    } else {
        $this->totalQty += 1;
        $this->totalPrice += $product->price;
    }
    $this->items[$product->id]['qty'] += 1;
}

【问题讨论】：

标签： arrays laravel

【解决方案1】：

查看完整的课程以及您对add() 函数的使用会很有帮助。

如果$this->items 是null，我希望您传递给构造函数的$cart 对象具有null 项。

假设这是你的整个班级；

class Cart
{
  public function __construct($cart = null)
  {
    if ($cart) {
      $this->items = $cart->items;
      $this->totalPrice = $cart->totalPrice;
      $this->totalQty = $cart->totalQty;
    } else {
      $this->items = [];
      $this->totalQty = 0;
      $this->totalPrice = 0;
    }
  }

  public function add($product)
  {
    $item = [
      'id' => $product->id,
      'name' => $product->name,
      'price' => $product->price,
      'qty' => 0,
      'image' => $product->image,
    ];
    if (!array_key_exists($product->id, $this->items)) {
      $this->items[$product->id] = $item;
      $this->totalQty += 1;
      $this->totalPrice += $product->price;
    } else {
      $this->totalQty += 1;
      $this->totalPrice += $product->price;
    }
    $this->items[$product->id]['qty'] += 1;
  }
}

如果您考虑下面的 sn-p，此代码将给出您遇到的相同错误。

$product = (object) [
  'id' => 1,
  'name' => 'product',
  'price' => 100,
  'qty' => 0,
  'image' => 'image.jpg',
];

$existingCart = (object) [
  'items' => null, // this is most likely your issue
  'totalPrice' => 1000,
  'totalQty' => 1,
];

$cart = new Cart($existingCart);

$cart->add($product); // TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given

如果$cart->items属性中有项目，则不会抛出错误；

$product = (object) [
  'id' => 1,
  'name' => 'product',
  'price' => 100,
  'qty' => 0,
  'image' => 'image.jpg',
];

$existingCart = (object) [
  'items' => [
    'product-1' => $product, // we actually have an array here of products. An empty array would also be fine
  ],
  'totalPrice' => 1000,
  'totalQty' => 1,
];

$cart = new Cart($existingCart);

$cart->add($product); // null

通过在构造函数中使用dd() 或print_r() 来检查构造函数输入以检查$cart 参数。

【讨论】：