Dart 将 Map<dynamic, dynamic> 转换为 Map<String, List<String>>

Question

如何转换成这样Map:

Map<dynamic, dynamic> a = {2022-04-10: [8:00, 15:00]}; //No quotes

获得：

Map<String, List<String>> b = {"2022-04-10": ["8:00", "15:00"]};

我试过这样做，但对我不起作用。没有错误，但是如果你调用 print，什么也不会发生：

String str = '{2022-04-10: [8:00, 15:00]}';
final Map<dynamic, dynamic> dynamicMapFromJson = json.decode(str);
Map<String, List<String>> schedule = dynamicMapFromJson.cast<String, List<String>>();

我正在从 Firebase 教授这张地图：

await FirebaseFirestore.instance
        .collection('call')
        .get()
        .then((QuerySnapshot querySnapshot) {
      for (var doc in querySnapshot.docs) {
        Map<String, List<String>> _schedule = doc.get('schedule');
      }
    });

Answer 1

你的地图是

Map<dynamic, dynamic> a = {"2022-04-10": ["8:00", "15:00"]};

可以通过两种方式转换

Map<dynamic, dynamic> a = {"2022-04-10": ["8:00", "15:00"]};
Map<String, List<String>> converted = {};

// 1st way:
for (var item in a.keys)
  converted[item.toString()] = List<String>.from(a[item]);
 
// 2nd way:
for (var item in a.keys)
{
  List<String> _new = [];
  for (var newItem in List.from(a[item]))
     _new.add(newItem.toString());
  converted[item.toString()] = _new;
}

Answer 2

您可以使用正则表达式的魔力 “它不是真正完美的表达式” 但它适用于您的情况在这里你可以匹配日期 yyyy-mm-dd 和 hh: mm 然后用引号替换

String str = '{2022-04-10: [8:00, 15:00]}';

 var stringify =  str.replaceAllMapped(RegExp("([0-9]{4}-[0-9]{2}-[0-9]{2})|([0-9]{0,2}:[0-9]{0,2})"), (match) => "\"${match.group(0)}\""); 
 //This step just for replace ":" with normal :
 stringify = stringify.replaceAll("\":\"",":");
 print("value:  $stringify");

  
 final Map dynamicMapFromJson = json.decode(stringify);
 print(dynamicMapFromJson);

Try the code here

Dart 将 Map<dynamic, dynamic> 转换为 Map<String, List<String>>

Dart convert Map<dynamic, dynamic> to Map<String, List<String>>

dart

flutter

google-cloud-firestore