Dart:
Working with JSON
How to:
Dart provides built-in support for JSON with the dart:convert library, making it straightforward to encode and decode JSON. Below are examples showcasing basic operations:
Parsing JSON String to Dart Object:
import 'dart:convert';
void main() {
// Example JSON string
String jsonString = '{"name": "John", "age": 30, "email": "[email protected]"}';
// Decoding JSON to Dart Map
Map<String, dynamic> user = jsonDecode(jsonString);
print('Hello, ${user['name']}! You are ${user['age']} years old.');
// Output: Hello, John! You are 30 years old.
}Encoding Dart Object to JSON String:
import 'dart:convert';
void main() {
// Example Dart object
Map<String, dynamic> user = {
'name': 'Jane',
'age': 25,
'email': '[email protected]'
};
// Encoding Dart Map to JSON
String jsonString = jsonEncode(user);
print(jsonString);
// Output: {"name":"Jane","age":25,"email":"[email protected]"}
}Using json_serializable for Complex Models:
For complex data models, manual serialization can be cumbersome. The json_serializable package automates this process. It requires additional setup, including adding dependencies to your pubspec.yaml and creating build files. After setup, you can use it as follows:
- Define a model with annotations:
import 'package:json_annotation/json_annotation.dart';
part 'user.g.dart';
@JsonSerializable()
class User {
String name;
int age;
String email;
User({required this.name, required this.age, required this.email});
factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
Map<String, dynamic> toJson() => _$UserToJson(this);
}- Generate the serialization boilerplate:
Use the build runner command to generate the
user.g.dartfile:
flutter pub run build_runner build- Use your model:
void main() {
// Parsing JSON to User
Map userMap = jsonDecode('{"name": "John", "age": 30, "email": "[email protected]"}');
User user = User.fromJson(userMap);
print('User: ${user.name}, Age: ${user.age}');
// Output: User: John, Age: 30
// Converting User back to JSON
String jsonString = jsonEncode(user.toJson());
print(jsonString);
// Output: {"name":"John","age":30,"email":"[email protected]"}
}These examples illustrate basic and advanced JSON interactions in Dart, empowering developers to handle data serialization tasks in their applications seamlessly.