Book Image

Swift Essentials

By : Alex Blewitt, Bandlem Limited
Book Image

Swift Essentials

By: Alex Blewitt, Bandlem Limited

Overview of this book

Table of Contents (16 chapters)
Swift Essentials
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Custom graphics with drawRect


Subclasses of UIView can implement their own custom graphics by providing a drawRect method that implements the custom drawing routines. The drawRect method takes a CGRect argument, which indicates the area to draw in, but the actual drawing commands are performed on a Core Graphics context, which is represented by the CGContext class and can be obtained by a call to UIGraphicsGetCurrentContext.

The Core Graphics context represents a drawable area in iOS and is used for printing as well as drawing graphics. Each view is responsible for drawing itself; the rectangle will either be the full area (for example, the first time that a view is drawn) or it might be a subset of the area (for example, when a dialog has been shown and then subsequently removed).

Core Graphics is a C-based interface (rather than Objective-C based), so the API is exposed as a set of functions beginning with the UIGraphics prefix. As with other drawing APIs, the program can set the current...