Month: February 2018

Xcode: using the “Debug executable” checkbox to step through app release versions

Here’s an Xcode setting, but what does it do for developers?

There’s a checkbox named “Debug executable” on the “Info” pane for Xcode’s “Debugging Options in the Scheme Editor.” Why is there such a dearth of information on this checkbox, a “simple” Xcode scheme option? Apple has little to say about the feature. Information about it is scarce on the web. I’ve heard all sorts of different opinions about what the checkbox does or doesn’t do. (Some of this may be exacerbated by Apple releasing buggy versions of Xcode.)

I’ll discover and explain, using the scientific method, how the “Debug executable” checkbox works. You may be thinking this is much ado about one checkbox, but my purpose is to get you to think about and learn a lot about debugging with Xcode. The absolute best developers are the ones with great and instinctive debugging, nay, TROUBLESHOOTING, skills.

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Swift 4 property observers: responding to changes in property values and managing state

Swift tutorials by iosbrain.comWe’re going to learn about a feature of Swift called “property observers” that help developers manage app state. You can easily add code to monitor changes to Swift native type property values as well as your own custom type property values. Remember that you can gain insight into an application by looking at its state: the data values stored in all properties of the app at a specific point in time. Getting a grip on app state, therefore managing complexity, is one of the biggest challenges in computer science. Property observers are one technology that help you get a grip. In today’s article, I’ll explain this Swift feature, demonstrate its usage with runnable examples of Swift code, show you how I built an app which relies on property observers, and provide you a list of other Swift technologies that help you manage app state and complexity. Here’s my sample app in action:

Download the Xcode 9 project and playground, both written in Swift 4, from GitHub so you can follow along with my discussion.

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I’ve started writing iOS tutorials for AppCoda as a freelancer

It is my great honor and privilege to have joined the tutorials team at AppCoda.com as a freelancer. My first tutorial, “Swift 4 Generics: How to Apply Them in Your Code and iOS Apps,” was published yesterday, and was originally published here on my own site at this link. I am looking forward to publishing many more tutorials for you, my most loyal readers, at AppCoda and here on iOSBrain.com. Note: If I cross-post an article on AppCoda and here, the article will appear first on AppCoda. Thank you AppCoda!

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Debugging: symbolicating crash reports manually (stack trace, backtrace)

Swift tutorials by iosbrain.comToday, we’ll talk about manually symbolicating iOS and OS X application “crash reports.” Why? When you hear about a crash in one of your apps from a customer, the first thing you should do is try to get a copy of the crash report. But there are times when you get crash reports that aren’t automatically symbolicated, or that you can’t symbolicate by dragging into Xcode, or are partially symbolicated. When not symbolicated, you’re reading numeric addresses when you want to be reading code, like your function/class names. There are workarounds and we’ll discuss one today. Download the sample Xcode 9 project written in Objective-C to follow along. What’s a crash report, anyway? According to Apple:

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NSNotificationCenter in Swift 4: Intra-app communication, sending, receiving, listening, stop listening for messages

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

The topic today is how to communicate between objects within an app, specifically using iOS’s NSNotificationCenter. In the last post, “Tutorial: delegates and delegation in Swift 4,” I used delegation to communicate between two objects. In the code I wrote for the last article, the app’s main (and only) view controller waited to display an image. The image was not included in the app bundle, rather downloaded from a NASA website. I created a class that downloaded the image file. The view controller was informed that the image was finished downloading and ready to display using a technique called “delegation.” Here, we’ll modify the delegation tutorial code to work with NSNotificationCenter instead. The image downloading class will notify the view controller that the image has finished downloading by sending a notification (message).

I will show you: 1) a one-post-to-one-observer notification; and, 2) a broadcast, where one post is received by many observers. Download the project and follow along in Xcode. Here’s the app we’ll build:

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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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