JSON parsing (jsonDecode) in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the jsonDecode function do in Flutter?

It converts a JSON string into a Dart object, like a Map or List, so you can use the data in your app.

beginner

Which Dart type does jsonDecode return when parsing a JSON object?

It returns a Map<String, dynamic> representing the JSON object.

intermediate

Why should you handle exceptions when using jsonDecode?

Because if the JSON string is invalid or malformed, jsonDecode throws a FormatException. Handling it prevents app crashes.

beginner

How do you import the library needed to use <code>jsonDecode</code> in Flutter?

You import it with <code>import 'dart:convert';</code> at the top of your Dart file.

beginner

What is a real-life example of using jsonDecode in a mobile app?

When your app gets data from a web server in JSON format, you use jsonDecode to turn that data into Dart objects to show on the screen.

What type of data does jsonDecode expect as input?

A A JSON formatted string

B A Dart Map object

C A List of integers

D An XML string

jsonDecode takes a JSON string and converts it to Dart objects.

Which Dart type is returned when jsonDecode parses a JSON array?

A Map<String, dynamic>

B int

C List<dynamic>

D String

A JSON array becomes a Dart List when decoded.

What happens if you try to decode an invalid JSON string with jsonDecode?

A Throws a FormatException

B Returns null

C Returns an empty Map

D Automatically fixes the JSON

Invalid JSON causes jsonDecode to throw a FormatException.

Which import is required to use jsonDecode in Flutter?

A import 'package:flutter/material.dart';

B import 'dart:convert';

C import 'dart:io';

D import 'package:http/http.dart';

jsonDecode is in the dart:convert library.

Which of these is a common use of jsonDecode in mobile apps?

A To convert Dart objects to JSON strings

B To handle user input events

C To style UI components

D To parse JSON data received from a web API

jsonDecode is used to parse JSON data from APIs into Dart objects.

Explain how you would use jsonDecode to handle JSON data from a web API in Flutter.

Think about the steps from receiving a JSON string to using it safely in your app.

Describe what types of Dart objects you get after decoding JSON objects and arrays with jsonDecode.

Consider the JSON structure and how it maps to Dart types.