Author: Andrew Jaffee

Avid and well-published author, software engineer, designer, and developer, now specializing in iOS mobile app development in Objective-C and Swift, but with a strong background in C#, C++, .NET, JavaScript, HTML, CSS, jQuery, SQL Server, MySQL, Oracle, Agile, Test Driven Development, Git, Continuous Integration, Responsive Web Design, blah, blah, blah ... Did I miss any fad-based catch phrases? My brain avatar was kindly provided by https://icons8.com under a Creative Commons Attribution-NoDerivs 3.0 Unported license.

Tutorial: delegates and delegation in Swift 4

The original article – Understanding Delegates and Delegation in Swift 4 was published on appcoda.com.

[Download Xcode 9 project with full Swift 4 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 Swift 4, with full source code. My intent here is to show you how delegation works without getting bogged down in some crazy complex example. To help you become the best of the best, I’m going to introduce you to one of the greatest design tools to aid in object-oriented software development, UML. I’ll show you a UML diagram that I drew up to design and document the implementation of the delegation design pattern used in the sample app we’ll build together. Download the Xcode 9 project with full Swift 4 source from GitHub to follow along.

(Note: compare this post’s approach of using delegation with my next post’s approach of using NSNotificationCenter — to accomplish the same goal.)

I’ll show you how to build a user interface (UI) helper, a class that downloads a file at a specified URL. Most importantly, I’ll show you how, through delegation, a UIViewController subclass can be notified by the helper that an image file has finished downloading, and then the view controller can display the image on screen. For the sake of simplicity and clarity, we’ll pretend that Swift has minimal support for downloading a file from a URL. We’ll manually wire up the notification that the file has finished downloading using the delegation design pattern. Here’s the app we’ll build:

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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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Fix for IBOutlet, IBAction connections disappearing in Xcode 9

You’ve been working on your billion dollar app happily for days or weeks. It’s Monday morning, you open up Xcode 9 to get back to work and — dang, bummer — all your IBOutlet and IBAction connections look like they’ve been disconnected (see image below):

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Writing expressive, meaningful, and readable code in Swift 4

Let’s talk about creating understandable and maintainable code in Swift 4, code that can be easily read by other programmers, can be readily debugged, can be reused, and can be enhanced and extended in the future. We’re going to limit today’s discussion to: 1) how best to come up with good names for functions and how best to name their arguments, parameters, and argument labels, and 2) how to use meaningful and descriptive variable (var) names — and constant (let) and enumeration (enum) names, etc. The goal is to create code that reads as to close to English as possible.

You may believe that this topic is overly simplistic or pedantic, but sometimes it’s the “little things” in life that really matter — especially when you have applications that are made up of millions of lines of code, made up of “little things” like function definitions and function calls.

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Xcode tidbits: Open as Hex, Open As Source Code, (Git) line endings, and text encoding

With this article, I’m starting a series about all the goodies — useful tools — that can be found in Xcode. Some of these tidbits are tools everyone knows about while others are barely documented to undocumented. For example, how many of you know that you can view, inspect, and debug all your Auto Layout constraints live during app execution using the “Debug View Hierarchy” Xcode feature? I discussed that feature in detail in this article, “Troubleshooting Auto Layout using Xcode’s Debug View Hierarchy.” Today, we’ll discover two editors that ship with Xcode, the “Open As > Hex” and “Open As > Source Code” editors, both only available by right-clicking on files in the “Project Navigator” to reveal a contextual menu.

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Understanding Swift 4 protocols and using them in your apps

NOTE: Learn all about protocol-oriented programming in Swift here, here, and here.

[Download two Xcode 9 playgrounds with full Swift 4 source from GitHub.]

We’re going to talk about “protocols” in the Swift 4 language today. I’ll explain them conceptually, and then we’ll start coding protocols with a simple example. We’ll then create our own versions of the Apple built-in Equatable and Comparable protocols, and apply them to two real-world classes, one for tracking financial securities and one for representing geometric lines/vectors. Finally, we’ll test our geometric “Line” class in a type of Swift playground that supports rendering user interface components (like UIView) live in the simulator. But first, please ponder the layman’s definition of the word “protocol” before moving on:

… The official procedure or system of rules governing affairs of state or diplomatic occasions. …

The accepted or established code of procedure or behaviour in any group, organization, or situation. …

A procedure for carrying out a scientific experiment…

Swift Protocols

Apple’s “The Swift Programming Language (Swift 4.0.3)” documentation states:

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Building Swift 4 frameworks and including them in your apps (Xcode 9)

Let’s talk about Swift 4 frameworks, one method for packaging, reusing, and sharing code. We’ll build our own framework and then include it in our own app. We could’ve talked about static libraries, but frameworks offer more advanced features — and will let us expand on code maintainability options in future discussions. (If you want to have that static versus dynamic library discussion, read this excellent article, but we won’t be debating the topic herein.) From Apple (my emphasis added):

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Understanding Swift 4 generics and applying them in your code

The original article – Swift 4 Generics – was published on appcoda.com.

Swift tutorials by iosbrain.comQuestion 1: Can I write one Swift function that can find the index/position of any specific instance of any type stored in any array that stores objects of that type? Question 2: Can I write one Swift function that can determine if any specific instance of any type exists in any array that stores objects of that type? When I say “any type,” I mean including custom types (like classes) that I define myself. NOTE: Yes, I know that I could use the Swift Array type’s built-in functions, index and contains, but I’ll be using simple example code today to illustrate some points about Swift generics.

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Typical Git/GitHub workflow tutorial: configure, clone, commit, stage, push, pull, status

Introduction

Suppose your supervisor or customer gives you a new project to work on: “I want you to start helping out on my iOS project, ‘Blocks-in-Objective-C.’ Please get a copy of the code, make these changes, test, and then check your new code into the repo. By the way, we’re using Git for source control.” Have you used Git before? Do you know it well? (Does anyone truly understand Git?) Today, I’ll show you how to accomplish that task just assigned by your supervisor or customer.

Requirements

Since this is an iOS blog, I’m assuming you’ve installed Xcode and therefore Git is installed on your Mac. (If you need to install Git, click here.)

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Polymorphism in Swift 3: manipulate multiple related controls with one IBOutlet and one IBAction

How would you enable or disable multiple user interface controls using one IBOutlet and one IBAction? For example, you might need to disable a UITextBox and UISegmentedControl because a user’s login has expired. Perhaps a user hasn’t filled in some required fields on a form, so you want to disable several buttons. Watch the following video to see how I built a Swift 3 app to use a UISwitch to enable or disable four controls all at one time — and I demonstrated the object-oriented programming (OOP) principle of polymorphism:

Refresh your memory about OOP and inheritance.

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