Summary - JSON parsing

Combine jsonDecode and nested access to handle API responses.

Decoding an API response as a whole

An API response usually mixes nested objects and arrays. First you decode the string into a Map<String, dynamic> with jsonDecode, then access fields with square brackets.

const yanit = '{"kullanici": {"ad": "Cem"}, "arkadaslar": ["Ali", "Veli"]}';
final m = jsonDecode(yanit) as Map<String, dynamic>;
print(m['kullanici']['ad']);  // Cem
print((m['arkadaslar'] as List)[0]);  // Ali

Because the content can have mixed types, casting with as makes access safer.

Exercise Process the API response

Decode the string yanit with jsonDecode. First print the 'ad' value, then print the first element of the 'arkadaslar' list with print.

Show example solution

import 'dart:convert';

void main() {
  const yanit = '{"ad": "Deniz", "arkadaslar": ["Selin", "Mert"]}';
  final m = jsonDecode(yanit);
  print(m['ad']);
  print((m['arkadaslar'] as List)[0]);
}

Test yourself

If the 'arkadaslar' field in an API response is an array, how do you reach the first friend after jsonDecode?
- m['arkadaslar']['ad']
- m[0]['arkadaslar']
- jsonEncode(m['arkadaslar'])
- (m['arkadaslar'] as List)[0]
Show answer

(m['arkadaslar'] as List)[0] — Since arkadaslar is an array, you first cast it to List and then access by index. jsonEncode serializes data instead of reading it; m['arkadaslar']['ad'] would require Map access; m[0] applies to a list, not to the root Map.

Get the second friend

import 'dart:convert';

void main() {
  const s = '{"ad": "Cem", "arkadaslar": ["Ali", "Veli"]}';
  final m = jsonDecode(s);
  final ikinciArkadas = (m['arkadaslar'] as List)[____];
  print(ikinciArkadas);
}

Show answer

import 'dart:convert';

void main() {
  const s = '{"ad": "Cem", "arkadaslar": ["Ali", "Veli"]}';
  final m = jsonDecode(s);
  final ikinciArkadas = (m['arkadaslar'] as List)[1];
  print(ikinciArkadas);
}

JSON parsing summary

jsonDecode

Converts a JSON string to a Map
m['kullanici']['ad']

Reads a value from nested objects
(m['arkadaslar'] as List)[0]

Accesses the first element of the list
dart:convert

Library of jsonDecode and jsonEncode

Next lesson: What is a model class?

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