Flutter中如何从API返回的对象数组获取最新dateoflastinsp日期

你在Flutter项目中从服务器拿到了包含巡检记录的JSON数据，需要从rows数组里提取出最新的dateoflastinsp日期，具体实现可以按以下步骤来：

首先，服务器返回的JSON数据如下：

{"drainageid": "","datacount": 98359,"resultcount": 98359,"page": "","rows": [{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": null,"dateofinsp": "2001-10-10T00:00:00","inspby": "SAW/ZAG"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2001-10-10T00:00:00","dateofinsp": "2002-09-24T00:00:00","inspby": "SAW+NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2002-09-24T00:00:00","dateofinsp": "2003-09-18T00:00:00","inspby": "SAW/NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2003-09-18T00:00:00","dateofinsp": "2004-09-08T00:00:00","inspby": "SAW/NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2004-09-08T00:00:00","dateofinsp": "2005-05-05T00:00:00","inspby": "MZB/ASMG"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2005-05-05T00:00:00","dateofinsp": "2006-05-04T00:00:00","inspby": "MZB/ASZ"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2006-05-04T00:00:00","dateofinsp": "2007-05-09T00:00:00","inspby": "Ahmad/Haizul"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2007-05-09T00:00:00","dateofinsp": "2008-05-07T00:00:00","inspby": "Harzazi/Zulkornain"}]}

实现步骤 #

1. 解析JSON数据：用dart:convert里的jsonDecode把服务器返回的字符串转成Map对象，再提取出rows列表。
2. 过滤无效数据：排除dateoflastinsp为null的条目，避免后续转换出错。
3. 转换日期格式：把字符串类型的日期转成DateTime对象，这样才能进行日期比较。
4. 筛选最新日期：遍历转换后的日期列表，找出最大的那个（也就是最新的日期），再按需转回字符串格式。

完整代码示例 #

import 'dart:convert';

void main() {
  // 服务器返回的JSON字符串
  String jsonStr = '{"drainageid": "","datacount": 98359,"resultcount": 98359,"page": "","rows": [{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": null,"dateofinsp": "2001-10-10T00:00:00","inspby": "SAW/ZAG"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2001-10-10T00:00:00","dateofinsp": "2002-09-24T00:00:00","inspby": "SAW+NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2002-09-24T00:00:00","dateofinsp": "2003-09-18T00:00:00","inspby": "SAW/NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2003-09-18T00:00:00","dateofinsp": "2004-09-08T00:00:00","inspby": "SAW/NBN"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2004-09-08T00:00:00","dateofinsp": "2005-05-05T00:00:00","inspby": "MZB/ASMG"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2005-05-05T00:00:00","dateofinsp": "2006-05-04T00:00:00","inspby": "MZB/ASZ"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2006-05-04T00:00:00","dateofinsp": "2007-05-09T00:00:00","inspby": "Ahmad/Haizul"},{"id": "DR/C1/IC/H/-/GPG/PU/-/RCP/01","dateoflastinsp": "2007-05-09T00:00:00","dateofinsp": "2008-05-07T00:00:00","inspby": "Harzazi/Zulkornain"}]}';
  
  // 解析JSON
  Map<String, dynamic> data = jsonDecode(jsonStr);
  List<dynamic> rows = data['rows'];
  
  // 过滤并转换日期
  List<DateTime> validDates = rows
      .where((row) => row['dateoflastinsp'] != null)
      .map((row) => DateTime.parse(row['dateoflastinsp']))
      .toList();
  
  // 处理空列表情况
  if (validDates.isEmpty) {
    print('没有有效的dateoflastinsp日期');
    return;
  }
  
  // 找出最新日期
  DateTime latestDate = validDates.reduce((a, b) => a.isAfter(b) ? a : b);
  
  // 输出结果，可按需转成字符串格式
  print('最新的dateoflastinsp日期：${latestDate.toIso8601String()}');
}

注意事项 #

• 如果服务器返回的日期格式不是标准ISO8601，需要用intl包的DateFormat来解析，不过你的示例里是标准格式，直接用DateTime.parse就行。
• 一定要处理validDates为空的情况，避免调用reduce时抛出异常。

内容的提问来源于stack exchange，提问作者user21497668