Book Image

Flutter Cookbook

By : Simone Alessandria, Brian Kayfitz
4 (1)
Book Image

Flutter Cookbook

4 (1)
By: Simone Alessandria, Brian Kayfitz

Overview of this book

“Anyone interested in developing Flutter applications for Android or iOS should have a copy of this book on their desk.” – Amazon 5* Review Lauded as the ‘Flutter bible’ for new and experienced mobile app developers, this recipe-based guide will teach you the best practices for robust app development, as well as how to solve cross-platform development issues. From setting up and customizing your development environment to error handling and debugging, The Flutter Cookbook covers the how-tos as well as the principles behind them. As you progress, the recipes in this book will get you up to speed with the main tasks involved in app development, such as user interface and user experience (UI/UX) design, API design, and creating animations. Later chapters will focus on routing, retrieving data from web services, and persisting data locally. A dedicated section also covers Firebase and its machine learning capabilities. The last chapter is specifically designed to help you create apps for the web and desktop (Windows, Mac, and Linux). Throughout the book, you’ll also find recipes that cover the most important features needed to build a cross-platform application, along with insights into running a single codebase on different platforms. By the end of this Flutter book, you’ll be writing and delivering fully functional apps with confidence.
Table of Contents (17 chapters)
About Packt

How it works...

A modern programming language wouldn't be complete without closures, and Dart is no exception. To oversimplify this, a closure is a function that is saved to a variable that can be called later. They are often used for callbacks, such as when the user taps a button or when the app receives data from a network call.

We showed two ways to define closures in this recipe:

  • Function prototypes
  • typedefs

The easiest and most maintainable way to work with closures is with the typedef keyword. This is especially true if you are planning on reusing the same closure type multiple times; then, using typedefs will make your code more succinct:

typedef NumberGetter = int Function();

This defines a closure type called NumberGetter, which is a function that is expected to return an integer:

int powerOfTwo(NumberGetter getter) {
return getter() * getter();

The closure type is then used in this function, which will call the closure twice and then multiply the result:

final getFour = () => 4;
squared = powerOfTwo(getFour);

In this line, we call the function and provide our closure, which returns the number 4. This code also uses the fat arrow syntax, which allows you to write any function that takes up a single line without braces. For single-line functions, you can use the arrow syntax, =>, instead of brackets. 

The getFour line without the arrow is equivalent to writing the following:

final getFour = () {
return 4;
// this is the same as:
final getFour = () => 4;

Arrow functions are very helpful for removing unneeded syntax, but they should only be used for simple statements. For complex functions, you should use the block function syntax.

Closures are probably one of the most cognitively difficult programming concepts. It may seem awkward to use them at first, but the only way for it to become natural is to practice using them several times.