android - Flutter:如何在 dart 上解析 json 嵌套映射

Question

这是我要解析的json文件:

{
    "Meta Data": {
        "1. Information": "Weekly Adjusted Prices and Volumes",
        "2. Symbol": "MSFT",
        "3. Last Refreshed": "2020-03-25",
        "4. Time Zone": "US/Eastern"
    },
    "Weekly Adjusted Time Series": {
        "2020-03-25": {
            "1. open": "137.0100",
            "2. high": "154.3300",
            "3. low": "132.5200",
            "4. close": "146.9200",
            "5. adjusted close": "146.9200",
            "6. volume": "235583286",
            "7. dividend amount": "0.0000"
        },
        "2020-03-20": {
            "1. open": "140.0000",
            "2. high": "150.1500",
            "3. low": "135.0000",
            "4. close": "137.3500",
            "5. adjusted close": "137.3500",
            "6. volume": "421347734",
            "7. dividend amount": "0.0000"
        },
}

我只是想获取日期、打开和关闭。我尝试在网上查找东西，但仍然无法做到这一点。

这是我的 TimeSeries 类:

class TimeSeries {
  final String date;
  final double open;
  final double close;

  TimeSeries({this.date, this.open, this.close});

  factory TimeSeries.fromJson(Map<String, dynamic> json) {
    return TimeSeries(
      date: json[''],
      open: double.parse(json['1. open']),
      close: double.parse(json['4. close']),
    );
  }
}

这些是我现在的功能:

Future getTimeSeries(String stock) async {
    print("Starting get request");
    http.get("https://www.alphavantage.co/query?function=TIME_SERIES_DAILY&symbol=MSFT&apikey=demo").then((res){
      print("received response.");
      var resObj = json.decode(res.body);
     }).catchError((e) {
      print("Failed to get response.");
    });
  }

Answer 1

试试这个。

class TimeSeries {
  final String date;
  final double open;
  final double close;

  TimeSeries({this.date, this.open, this.close});

  factory TimeSeries.fromJson(Map<String, dynamic> json, String indexDate) {
    return TimeSeries(
      date: indexDate,
      open: double.parse(json["Weekly Adjusted Time Series"][indexDate]['1. open']),
      close: double.parse(json["Weekly Adjusted Time Series"][indexDate]['4. close']),
    );
  }
}

并且您可以按如下方式调用构造函数

List<TimeSeries> datesList(json) {
   List<TimeSeries> dates;
   for (date in json["Weekly Adjusted Time Series"]) {
       dates.add(TimeSeries.fromJson(json, date));
    }
    return dates;
}