Sort Json in Flutter - json

Question

I get the following Json output from url:
{
"Meta Data": {
"1. Information": "FX Intraday (5min) Time Series",
"2. From Symbol": "USD",
"3. To Symbol": "TRY",
"4. Last Refreshed": "2020-12-18 21:55:00",
"5. Interval": "5min",
"6. Output Size": "Full size",
"7. Time Zone": "UTC"
},
"Time Series FX (5min)": {
"2020-12-18 21:55:00": {
"1. open": "7.6181",
"2. high": "7.6256",
"3. low": "7.6181",
"4. close": "7.6181"
},
"2020-12-18 21:50:00": {
"1. open": "7.6232",
"2. high": "7.6244",
"3. low": "7.6181",
"4. close": "7.6181"
},
"2020-12-18 21:45:00": {
"1. open": "7.6244",
"2. high": "7.6244",
"3. low": "7.6208",
"4. close": "7.6232"
},
"2020-12-18 21:40:00": {
"1. open": "7.6234",
"2. high": "7.6262",
"3. low": "7.6201",
"4. close": "7.6244"
},
.
.
.
} }
I need to sort the 'Time Series FX(5min)' values by the keys (date) in reverse order , so the first position has the latest date time. Then I want to extact the first (latest) 288 elements.
What I need in the returned list(s) is only the date time and the value of '4. close'
for example something like this:
list<String> Date_time = [2020-12-18 21:55:00, 2020-12-18 21:50:00, 2020-12-18 21:45:00,...]
list<double> values = [7.6181, 7.6181, 7.6232,...]
Here is part of the code:
void fetchDayValues() async {
final response = await http.get(
'https://www.alphavantage.co/query?function=FX_INTRADAY&from_symbol=' +
symbol.substring(0, 3) +
'&to_symbol=' +
symbol.substring(4) +
'&interval=5min&outputsize=full&apikey=NS8IP79OIRVVH7Q0');
if (response.statusCode == 200) {
final jsonInput = json.decode(response.body) as Map;
final data = jsonInput["Time Series FX (5min)"] as Map;
}
}
I looked at other answers but cannot find a solution to my problem. How to do it? Thanks

Answer 1

This code sorts the data by the date. It uses string comparison for simplicity.
You can try it on Dartpad.
import 'dart:convert';
void main() {
final raw_string = '''{"Time Series FX (5min)": {
"2020-12-18 21:50:00": {
"1. open": "7.6232",
"2. high": "7.6244",
"3. low": "7.6181",
"4. close": "7.6181"
},
"2020-12-18 21:55:00": {
"1. open": "7.6181",
"2. high": "7.6256",
"3. low": "7.6181",
"4. close": "7.6181"
},
"2020-12-18 21:40:00": {
"1. open": "7.6234",
"2. high": "7.6262",
"3. low": "7.6201",
"4. close": "7.6244"
},
"2020-12-18 21:45:00": {
"1. open": "7.6244",
"2. high": "7.6244",
"3. low": "7.6208",
"4. close": "7.6232"
}}}''';
final decoded = jsonDecode(raw_string)["Time Series FX (5min)"] as Map;
final sortedKeys = decoded.keys.toList()..sort((a,b)=> b.toString().compareTo(a.toString()));
final sortedValues = sortedKeys.map((k)=> decoded[k]["4. close"]).toList();
print(sortedKeys);
print(sortedValues);
}