jsonDecode
- Flutter course
- Intermediate
- Lesson 51/99
- 4 min
Parse a JSON string into a Map with jsonDecode.
Decode JSON with jsonDecode
JSON is the most common format for data coming from a server. In Dart you turn a JSON string into a Map with jsonDecode. This function lives in the dart:convert library.
import 'dart:convert';
const veri = '{"ad": "Ayşe", "yas": 28}';
final map = jsonDecode(veri);
print(map['ad']); // AyşeThe returned object is actually of type Map<String, dynamic>; the type of each value is determined at runtime.
Importing dart:convert
To use jsonDecode, add import 'dart:convert'; at the top of the file. This library is part of the Dart SDK; no extra package is needed.
import 'dart:convert';
void main() {
final s = '{"sehir": "İstanbul"}';
final m = jsonDecode(s) as Map<String, dynamic>;
print(m['sehir']); // İstanbul
}Specifying the type explicitly with as helps both the compiler and the reader.
Practice Print the name from JSON
Decode the string s with jsonDecode and print the value at the 'ad' key with print.
Starter code
import 'dart:convert';
void main() {
const s = '{"ad": "Deniz"}';
// JSON dizesini çöz ve 'ad' değerini yazdır
}Sample solution
import 'dart:convert';
void main() {
const s = '{"ad": "Deniz"}';
final m = jsonDecode(s);
print(m['ad']);
}Expected output
Deniz
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does the call jsonDecode('{"ad":"Ayşe"}') return?
- A Future
- A Widget
- An object of type Map<String, dynamic> Correct answer
- Always a String
Explanation: jsonDecode converts a JSON object to a Map and a JSON array to a List. Since the input is an object, the returned type is Map<String, dynamic>.
2 Decode the JSON string
import 'dart:convert';
void main() {
const s = '{"ad": "Ece"}';
final m = ____(s);
print(m['ad']);
}import 'dart:convert';
void main() {
const s = '{"ad": "Ece"}';
final m = jsonDecode(s);
print(m['ad']);
}Explanation: jsonDecode is the JSON decoding function in dart:convert; it turns the string into a Map.
3 dart:convert parts
| Term | Meaning |
|---|---|
jsonDecode |
Converts a JSON string to an object |
dart:convert |
The library to import |
Map<String, dynamic> |
Dart equivalent of a JSON object |
m['ad'] |
Access to the 'ad' value in the Map |