Dart解析嵌套映射json

import 'dart:convert';

String jsonString = '{"name": "John", "age": 30, "address": {"city": "New York", "country": "USA"}}';
Map<String, dynamic> jsonMap = json.decode(jsonString);

String name = jsonMap['name'];
int age = jsonMap['age'];
String city = jsonMap['address']['city'];
String country = jsonMap['address']['country'];

class Person {
  String name;
  int age;
  Address address;

  Person({this.name, this.age, this.address});

  factory Person.fromJson(Map<String, dynamic> json) {
    return Person(
      name: json['name'],
      age: json['age'],
      address: Address.fromJson(json['address']),
    );
  }
}

class Address {
  String city;
  String country;

  Address({this.city, this.country});

  factory Address.fromJson(Map<String, dynamic> json) {
    return Address(
      city: json['city'],
      country: json['country'],
    );
  }
}

String jsonString = '{"name": "John", "age": 30, "address": {"city": "New York", "country": "USA"}}';
Map<String, dynamic> jsonMap = json.decode(jsonString);
Person person = Person.fromJson(jsonMap);