How Does Dart Handle JSON Data?

Handling JSON data in Dart primarily involves two steps: parsing and encoding. Dart provides the built-in json library to handle these operations. Below are the specific steps and examples:

1. Import the dart:convert library

First, you need to import Dart's dart:convert library, which contains the tools required for handling JSON:

dart
import 'dart:convert';

2. JSON Parsing (Decoding)

Convert JSON strings to Dart Maps or Lists. This is typically used when retrieving API response data:

dart
String jsonString = '{"name": "John", "age": 30}';
Map<String, dynamic> user = jsonDecode(jsonString);

print(user['name']);  // Output: John
print(user['age']);   // Output: 30

If JSON is an array:

dart
String jsonArray = '[{"name": "John"}, {"name": "Jane"}]';
List<dynamic> users = jsonDecode(jsonArray);

print(users[0]['name']);  // Output: John
print(users[1]['name']);  // Output: Jane

3. JSON Encoding (Serialization)

Convert Dart Maps or Lists to JSON strings. This is typically used for sending data to servers:

dart
Map<String, dynamic> data = {'name': 'John', 'age': 30};
String json = jsonEncode(data);

print(json);  // Output: {"name":"John","age":30}

4. Handling Complex JSON Structures

For more complex JSON structures, you may need to create model classes to represent the data and use libraries like json_serializable to simplify serialization and deserialization.

For example, create a User class and use json_serializable to automatically generate related JSON processing code:

dart
import 'package:json_annotation/json_annotation.dart';

part 'user.g.dart';

@JsonSerializable()
class User {
  String name;
  int age;

  User({required this.name, required this.age});

  factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
  Map<String, dynamic> toJson() => _$UserToJson(this);
}

Then, run the build command in your build_runner to generate the auto-generated code.

These steps outline the basic methods for handling JSON data in Dart. Using built-in functions and libraries can efficiently handle common data exchange formats in web development.