Nested JSON

Access nested Maps and read inner objects.

Accessing nested JSON

JSON responses usually contain nested objects. After jsonDecode, the value of the outer Map is itself a Map. You reach inner values by chaining square brackets.

const s = '{"kullanici": {"ad": "Ela", "yas": 22}}';
final m = jsonDecode(s) as Map<String, dynamic>;
final ad = m['kullanici']['ad'] as String;
print(ad);  // Ela

The inner Map is of type Map<String, dynamic> at runtime, so casting with as is safe.

Missing keys and the null risk

In nested access, reaching a missing key returns null instead of throwing. But applying another bracket on null throws a runtime error.

final m = jsonDecode('{"a": {}}') as Map<String, dynamic>;
print(m['a']['b']);  // null
print(m['a']['b']['c']);  // Error!

So with nested access you must make sure each step exists.

Exercise Print the city from nested JSON

Decode the string s with jsonDecode and print the inner 'sehir' value with print.

Show example solution

import 'dart:convert';

void main() {
  const s = '{"adres": {"sehir": "Bursa"}}';
  final m = jsonDecode(s);
  print(m['adres']['sehir']);
}

Test yourself

What does the expression m['kullanici']['ad'] return?
- The inner Map itself
- Only the outer Map
- The 'ad' value inside the inner Map
- It returns a List
Show answer

The 'ad' value inside the inner Map — m['kullanici'] gives the inner Map; the second ['ad'] step accesses the 'ad' value inside it. The result is the String 'Ela'.

Nested access

import 'dart:convert';

void main() {
  const s = '{"adres": {"sehir": "Ankara"}}';
  final m = jsonDecode(s);
  final sehir = m['adres'][____];
  print(sehir);
}

Show answer

import 'dart:convert';

void main() {
  const s = '{"adres": {"sehir": "Ankara"}}';
  final m = jsonDecode(s);
  final sehir = m['adres']['sehir'];
  print(sehir);
}

Nested access parts

m['kullanici']

Accesses the inner Map
['ad']

Gives the 'ad' value in the inner Map
as String

Casts the value to String
jsonDecode

Decodes the JSON string into a Map

Next lesson: List<dynamic>

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