flutter - 对列表中的值求和并删除重复项

Question

我有这个列表，想要求和并删除列表中的重复项

1 - 检查产品名称

2 - 如果产品名称等于，则对 NumberOfItems 求和

例如:

"Orders":[
    {
        "productName":"Apple",
        "NumberOfItems":"5"
    },
    {
        "productName":"Orange",
        "NumberOfItems":"2"
    },
    {
        "productName":"Egg",
        "NumberOfItems":"5"
    },
    {
        "productName":"Apple",
        "NumberOfItems":"3"
    },
    {
        "productName":"Orange",
        "NumberOfItems":"4"
    },
    {
        "productName":"Egg",
        "NumberOfItems":"9"
    },
]

我需要的结果如下所示:(总和取决于产品名称)

"Orders":[
    {
        "productName":"Apple",
        "NumberOfItems":"8"
    },
    {
        "productName":"Orange",
        "NumberOfItems":"6"
    },
    {
        "productName":"Egg",
        "NumberOfItems":"14"
    },
]

Answer 1

final orders = data["Orders"] as List;
final mapped = orders.fold<Map<String, Map<String, dynamic>>>({}, (p, v) {
  final name = v["productName"];

  if (p.containsKey(name)) {
    p[name]["NumberOfItems"] += int.parse(v["NumberOfItems"]);
  } else {
    p[name] = {
      ...v,
      "NumberOfItems": int.parse(v["NumberOfItems"])
    };
  }

  return p;
});

final newData = {
  ...data,
  "Orders": mapped.values,
};

print(newData);

结果是:

{Orders: ({productName: Apple, NumberOfItems: 8}, {productName: Orange, NumberOfItems: 6}, {productName: Egg, NumberOfItems: 14})}