Category: UICollectionView

Tutorial: delegates and delegation in Objective-C

[Download Xcode 9 project with full Objective-C source from GitHub.]

Introduction

I’m going to talk about “delegates” and “delegation.” I’ll lead you through a simple example of implementing the delegation design pattern in Objective-C, with full source code, and then show you a more sophisticated scenario. My intent here is to show you how delegation works without getting bogged down in some crazy complex example. Download the Xcode 9 project with full Objective-C source from GitHub to follow along.

I’ll show you how to build a user interface (UI) component, a status/progress indicator, which you can display on screen for processing-intensive tasks… AND I’ll show you how you can customize the behavior of the indicator by using delegation. For example, when the indicator starts, you could disable your UI; when the indicator stops, you could re-enable your UI; and, when the user taps the indicator, you could cancel processing-intensive tasks. Here’s the app we’ll build:

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Using Swift extensions to manage complexity, improve readability, and increase extensibility (UICollectionView, protocols, and delegates)

[Download the full Xcode project from GitHub.]

Today, I’m going to show you how to leverage the Swift “extension” language feature to manage software complexity, improve code readability, and increase extensibility. We’ll also talk about delegates, data sources, and protocols as they are concepts essential to this tutorial. According to Apple’s “The Swift Programming Language (Swift 3.0.1):”

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UPDATE: The UICollectionView is much more than a grid or matrix

Get started by [downloading the full Xcode project from GitHub.]

Let’s talk about the UICollectionView, a rich, configurable, and powerful iOS user interface component. I will write code in Swift 3.0 to create a UICollectionView to which I can add, select/highlight, deselect/unhighlight, and remove UICollectionViewCell’s. I’ll show you that I can select, deselect, add, and remove one cell at a time, or multiple cells at a time. And most importantly, I’ll demonstrate the importance of the relationship between a UICollectionView and its data source, and the importance of keeping a UICollectionView and its data source synchronized. You can download my entire Xcode 8.2.1 project. Feel free to reuse my code as long as you follow the terms of the license agreement. Today, we’re going to build a basic but completely functional instance of the UICollectionView in Swift 3.0 as illustrated by the following video:

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