Book Image

Learning Xcode 8

By : Jak Tiano
Book Image

Learning Xcode 8

By: Jak Tiano

Overview of this book

Over the last few years, we’ve seen a breakthrough in mobile computing and the birth of world-changing mobile apps. With a reputation as one of the most user-centric and developer-friendly platforms, iOS is the best place to launch your next great app idea. As the official tool to create iOS applications, Xcode is chock full of features aimed at making a developer’s job easier, faster, and more fun. This book will take you from complete novice to a published app developer, and covers every step in between. You’ll learn the basics of iOS application development by taking a guided tour through the Xcode software and Swift programming language, before putting that knowledge to use by building your first app called “Snippets.” Over the course of the book, you will continue to explore the many facets of iOS development in Xcode by adding new features to your app, integrating gestures and sensors, and even creating an Apple Watch companion app. You’ll also learn how to use the debugging tools, write unit tests, and optimize and distribute your app. By the time you make it to the end of this book, you will have successfully built and published your first iOS application.
Table of Contents (23 chapters)
Learning Xcode 8
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Adding gestures from code


While implementing gestures from the storyboard is a simple and visual way to set up gestures, sometimes you'll need to get into the details and create them purely with code. In this section, we're going to look at how to do just that, by adding a pinch gesture recognizer that allows us to scale our image up and down.

Creating a gesture through code

The first thing we're going to need to do is create a property to hold our gesture. Since the gesture is going to be created outside of initialization, we are going to have to make it an implicitly unwrapped optional value (remember, that is shown with the exclamation mark after the variable name).

Note

Here's a quick refresher on optional values in Swift:

First, there's a standard variable, which must always contain a value:

var view: UIView

Then, there's an optional variable, which may or may not have a value:

var view: UIView?

This means we need to unwrap the value every time we use it, to make sure there is a value inside...