Question

如果产品不存在，我愿意通过使用req.params.cart_id查找现有购物车并更新数组中的对象来更新现有购物车推新产品

这是我的猫鼬模式

public class LargestNextGaussian
{
    public static void main(String[] args)
    {
        // Random#nextDouble is implemented as 
        //   (((long)next(26) << 27) + next(27)) / (double)(1L << 53)
        // The "baseValue" here refers to the value that
        // is obtained by combining the results of the 
        // two calls to "next"

        long baseValueForV1 = 
            0b10000000000000000000000000000000000000000000000000001L;
        double valueForV1 = 
            baseValueForV1 / (double)(1L << 53);

        long baseValueForV2 = 
            0b10000000000000000000000000000000000000000000000000000L;
        double valueForV2 = 
            baseValueForV2 / (double)(1L << 53);

        // As of Random#nextGaussian:
        double v1, v2, s;
        do {
            v1 = 2 * valueForV1 - 1;
            v2 = 2 * valueForV2 - 1;
            s = v1 * v1 + v2 * v2;
        } while (s >= 1 || s == 0);
        double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
        double result = v1 * multiplier;

        System.out.println("baseValueForV1 " + Long.toBinaryString(baseValueForV1));
        System.out.println("baseValueForV2 " + Long.toBinaryString(baseValueForV2));
        System.out.println("valueForV1     " + valueForV1);
        System.out.println("valueForV2     " + valueForV2);
        System.out.println("v1             " + v1);
        System.out.println("v2             " + v2);
        System.out.println("s              " + s);
        System.out.println("multiplier     " + multiplier);
        System.out.println("result         " + result);
        System.out.println();
    }
}

让我说我有一个购物车：

baseValueForV1 10000000000000000000000000000000000000000000000000001
baseValueForV2 10000000000000000000000000000000000000000000000000000
valueForV1     0.5000000000000001
valueForV2     0.5
v1             2.220446049250313E-16
v2             0.0
s              4.930380657631324E-32
multiplier     5.4075951832589016E16
result         12.00727336061225

方法：

const shoppingCartSchema = mongoose.Schema({
    user_id: { type: String, required: true},
    cart_date: { type: String, required: true},
    activeCart: { type: Boolean, required: true },
    cart_content: [{
        product_id: { type: String, required: true},
        product_quantity: { type: Number, required: true},
    }]
})

如果更新结果应为：

{
    "_id" : ObjectId("5c6830c9a7e056443ce8befe"),
    "user_id" : "5c4e1a3cbc446733801b5a54",
    "cart_date" : "2019-02-16T15:48:25.464Z",
    "activeCart" : true,
    "cart_content" : [ 
        {
            "_id" : ObjectId("5c6830c9a7e056443ce8beff"),
            "product_id" : "1",
            "product_quantity" : 1
        }
    ],
    "__v" : 0
}

如果没有此类ID，则推送新产品：

router.post("/:update", (req, res, next) => { 
     const cart_id = req.params['update'];
     const product_id = req.body.product_id;
     Cart.update({"_id": cart_id},
     //{Here to find the cart_content[index].product_id}
     //{add +1 to product_quantity if product_id === to the req.product_id}
     //{if no such product_id, push the new product {
      "product_id": req.body.product_id,
      "product_quantity": req.body.product_quantity
}).then(response => {
console.log(response);
} 
});

Answer 1

正如@mzparacha在我的问题评论中所述，这是我的问题的答案： MongoDB Update array element (document with a key) if exists, else push

我认为您应该检查一下 stackoverflow.com/questions/41316056/…它正在描述解决方案对于相同的问题，但不是很有效

如何更新对象中的数组并推送（如果不存在）

1 个答案: