jsonDecode

Learn JSON parsing with jsonDecode.

jsonDecode

jsonDecode(String) comes from dart:convert and turns JSON text into a Dart object. The result is dynamic; usually cast to Map<String, dynamic> or List.

Example: var data = jsonDecode('{"name":"Ayşe","age":30}');. data['name'] yields 'Ayşe'. Malformed JSON throws FormatException.

Without a cast, data.name does not work; use data['name']. For type safety a fromJson factory is preferred (we will see it in L3).

Reading as a Map

A JSON object is cast to Map<String, dynamic>: var m = jsonDecode(s) as Map<String, dynamic>;. Then values are read via m['key'].

For nested objects, chain access: m['user']['name']. Each level is dynamic, so the compiler does not check; errors appear at runtime.

For lists, var list = jsonDecode(s) as List;. Elements are still dynamic; cast to a type.

Exercise Decode JSON text and print it

Add import 'dart:convert';. Inside main add var data = jsonDecode('{"name":"Ayşe","age":30}');. Add print(data['name']);.

Show example solution

import 'dart:convert';

void main() {
  var data = jsonDecode('{"name":"Ayşe","age":30}');
  print(data['name']);
}

Test yourself

What does jsonDecode return?
- dynamic
- Map
- String
- int
Show answer

dynamic — jsonDecode returns dynamic; cast to Map/List.

Decode JSON text

var data = ____(jsonText);

Show answer

var data = jsonDecode(jsonText);

Match the jsonDecode parts

jsonDecode

String → dynamic
Map<String, dynamic>

Object cast
data['key']

Value access
FormatException

Malformed JSON

Next lesson: jsonEncode

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