如何过滤 List<Map<String, dynamic>> 以在 Flutter 中获取值？

Question

我有一个 json 数据，我正在使用 await jsonDecode. 加载到 List<Map<String, dynamic>>。

例如，我有一个；

1. 金额 = 12500
2. 口径 = 24

我需要过滤儿子以获得成熟度值：689.19

另外，如果我的金额 = 12500 且价值 = 689.19，我需要获得 24 的口径。

如何过滤 List> json 数据以获取 Flutter 中的值？

[
   {"amount": "5000", "caliber": "12", "maturity":  "484.25"},
   {"amount": "5000", "caliber": "24", "maturity":  "275.67"},
   {"amount": "7500", "caliber": "12", "maturity":  "726.38"},
   {"amount": "7500", "caliber": "24", "maturity":  "413.51"},
   {"amount": "10000", "caliber": "12", "maturity":  "968.50"},
   {"amount": "10000", "caliber": "24", "maturity":  "551.35"},
   {"amount": "12500", "caliber": "12", "maturity":  "1210.63"},
   {"amount": "12500", "caliber": "24", "maturity":  "689.19"},
   {"amount": "15000", "caliber": "12", "maturity":  "1452.76"},
   {"amount": "15000", "caliber": "24", "maturity":  "827.03"},
   {"amount": "15000", "caliber": "12", "maturity":  "1694.89"},
   {"amount": "17500", "caliber": "24", "maturity":  "964.87"},
   {"amount": "17500", "caliber": "36", "maturity":  "727.66"},
   {"amount": "17500", "caliber": "48", "maturity":  "613.53"},
   {"amount": "17500", "caliber": "60", "maturity":  "548.44"},
   {"amount": "20000", "caliber": "12", "maturity":  "1937.01"},
   {"amount": "20000", "caliber": "24", "maturity":  "1102.71"}
]

更新： 在@Muldec 的帮助下，我终于明白了。

首先我将上面的儿子加载到列表中，如下所示。并应用@Muldec 答案，它就奏效了。

List<Map> myList = List<Map>.from(jsonDecode(jsonFastCalculation) as List);
final item = myList.firstWhere((e) => e['amount'] == '12500' && e['caliber'] == '24');
print(item['maturity']);

Answer 1

您可以使用列表中的firstWhere 或where 方法来获取您需要的Map 元素或Map 的列表，具体取决于您的搜索条件。

假设您绝对确定您的搜索条件只会给您一个项目（或者您只关心符合条件的第一个项目）这里有一个带有 firstWhere 的代码示例：

List<Map<String, dynamic>> myList = ....;

final item = myList.firstWhere((e) => e['amount'] == '12500' && e['caliber'] == '24');
print(item['maturity']);

根据数量和成熟度找到口径，只是在firstWhere方法中更改测试