main.dart

import 'dart:convert';

void main() {
  final johnJson = '{"name": "John Doe"}';

  final john = getUser(johnJson);

  final wrongJson = '{"name": "John Doe}';

  // this raises FormatException
  final wrong = getUser(wrongJson);
}

User getUser(String json) {
  // This can throw FormatException, however it's not handled
  final decoded = jsonDecode(json);

  final name = decoded['name'] as String;

  return User(name);
}

class User {
  final String name;

  const User(this.name);
}