I have a json String {"a":"{\"b\":7}"}. But it does not get decoded from the default library. I have written the following code:
import 'dart:convert';
void main() {
String a =
'{"a":"{\"b\":7}"}';
print(json.decode(a));
}
Please help to parse the json.
To work with JSON objects that have deep/multiple levels/recursive dot notation, then you can use a fantastic Dart package: g_json. I find it super easy and simple!
It doesn't use generated code as on Flutter recommended packages for JSON and these are complicated. Dart & Flutter teams have to improve.
I use a complex JSON object and your example and I show you how I access the data (you have to clean your JSON string, maybe your example is copied from a place that add extra double quotes " " on brackets).
Now, look at my code:
import 'dart:convert';
import 'package:g_json/g_json.dart';
void main() {
String jsonSimple = '{"a":"1"}';
// Get value from only one level JSON object.
final Map<String, dynamic> resultSimple = json.decode(jsonSimple);
print(resultSimple);
// Your example with some cleaning.
String jsonExample = jsonEncode({
"a": {"b": 7}
});
var resultDeep = JSON.parse(jsonExample);
print(resultDeep['a']['b'].rawString());
// Deep JSON object
// This is a real JSON data from api.openweathermap.org/data/2.5/weather?q=Barcelona&appid=<your_api_key>. You can try it on your browser, put it on the url and press `ENTER`.
String jsonWeather = jsonEncode({
"coord": {"lon": 2.159, "lat": 41.3888},
"weather": [
{
"id": 803,
"main": "Clouds",
"description": "broken clouds",
"icon": "04d"
}
],
"base": "stations",
"main": {
"temp": 291.21,
"feels_like": 291.11,
"temp_min": 289.53,
"temp_max": 293.62,
"pressure": 1016,
"humidity": 78
},
"visibility": 10000,
"wind": {"speed": 0.45, "deg": 212, "gust": 1.79},
"clouds": {"all": 75},
"dt": 1633360018,
"sys": {
"type": 2,
"id": 18549,
"country": "ES",
"sunrise": 1633326668,
"sunset": 1633368526
},
"timezone": 7200,
"id": 3128760,
"name": "Barcelona",
"cod": 200
});
print(jsonWeather);
// It prints: `String`
print(jsonWeather.runtimeType);
resultDeep = JSON.parse(jsonWeather);
print(resultDeep['wind']['speed'].rawString());
print(resultDeep['weather'][0]['main'].rawString());
// Extract data for each item of the array.
final List<dynamic> listJsonWeather = resultDeep['weather'].value;
List<WeatherEntity> listWeathers = [];
for (dynamic jsonWeather in listJsonWeather) {
listWeathers.add(WeatherEntity(
id: jsonWeather['id'].toString(),
title: jsonWeather['main'] as String,
overview: jsonWeather['description'] as String,
image: '<url>/${jsonWeather['icon']}',
));
}
}
The console prints the next outcome:
7
String
0.45
"Clouds"
Tips
You can use Postman to fetch API data from services. A very useful tool, trust me!
I implemented with your json string.
import 'dart:convert';
void main() {
String a = '{"a":"{\"b\":7}"}';
String b = a.replaceAll(RegExp(r'\\\""'), "\"");
b = b.replaceAll(RegExp(r'\"{'), "\{");
b = b.replaceAll(RegExp(r'\"}'), "\}");
print(b);
print(json.decode(b));
}
print(json.decode(json.decode(b)['a'])); throws the error.r'{"a":"{\"b\":7}"}' or '{"a":"{\\\"b\\\":7}"}'