jsonEncode
- Flutter course
- Intermediate
- Lesson 52/99
- 4 min
Serialize a Map to JSON string with jsonEncode.
Encode a Map to JSON with jsonEncode
To turn a Map back into a JSON string you use jsonEncode, also from dart:convert. It is handy when writing data to a file or sending it to a server.
import 'dart:convert';
final map = {'ad': 'Mert', 'yas': 30};
final s = jsonEncode(map);
print(s); // {"ad":"Mert","yas":30}The output is standard JSON with double quotes; the single quotes used in Dart become double quotes in JSON.
The type returned by jsonEncode
jsonEncode also turns numbers, strings, bools, and lists into JSON. The returned value is always a String in standard JSON format.
final s = jsonEncode([1, 2, 3]);
print(s); // [1,2,3]
print(s.runtimeType); // StringYou can later turn this string back into an object with jsonDecode.
Practice Print the Map as JSON
Encode the map into a JSON string with jsonEncode and print it with print.
Starter code
import 'dart:convert';
void main() {
final map = {'ad': 'Selin', 'yas': 25};
// map'i JSON dizesine çevir ve yazdır
}Sample solution
import 'dart:convert';
void main() {
final map = {'ad': 'Selin', 'yas': 25};
final s = jsonEncode(map);
print(s);
}Expected output
{"ad":"Selin","yas":25}
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What input does jsonEncode convert to a JSON string?
- A Widget tree
- A Future object
- Only an int
- A Map or List Correct answer
Explanation: jsonEncode converts a Map, List, number, string, or bool into a JSON string. The most common inputs are Map and List.
2 Encode the Map to JSON
import 'dart:convert';
void main() {
final map = {'sehir': 'İzmir'};
final s = ____(map);
print(s);
}import 'dart:convert';
void main() {
final map = {'sehir': 'İzmir'};
final s = jsonEncode(map);
print(s);
}Explanation: jsonEncode turns a Map into a standard JSON string.
3 Encoding parts
| Term | Meaning |
|---|---|
jsonEncode |
Converts an object to a JSON string |
String |
The type returned by jsonEncode |
{"ad":"Mert"} |
JSON output of the Map |
dart:convert |
Library that contains jsonEncode |