When working with Storyboards in Xcode, you’ll quickly find that you end up with varying amounts of different View Controllers (depending on the size of your app). Each of these needs to have a subclass created and then that subclass needs to be set as the View Controllers custom class. I’ll explain how that is done today, along with a way that you can find out exactly which type of View Controller you need to subclass.

Dragging Out the View Controller

For todays post, I’ll concentrate on the iPad as there are more View Controllers available for this device. The same principles apply for the iPhone although you wont be able to work with a SplitView Controller for example as this is an iPad only View Controller.

First of all, we need to drag out a View Controller to the storyboard. Lets go for the Table View Controller as pictured below.

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Bugs and errors can be frustrating to fix. Unfortunately, bugs are going to happen and you will see errors from time to time. Often errors appear because of the smallest detail.

One such error that popped up when I was building a project was the “Apple mach-o linker error”. It took me about an hour to eventually track it down. Here is what you will see on screen with this error:

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The documentation provided with Xcode is extremely helpful. It provides a lot of the information you’ll need to create apps for iOS devices. If you want to know how a particular class works, you look in the documentation to find exactly what is required and what methods are available. Understanding the documentation is one of the keys to being able to successfully start and finish writing an app.

How to Access the Documentation

You can access the documentation in several ways. This includes the web and the Xcode organizer as well as snippets of text that appear when typing in method names. Lets take a quick look at each so that you can get a good understanding of where to find the documentation.

On the web, you simply need to search for something like “corelocation class reference”. To find the official documentation, look for search results from the developer.apple.com domain name. Typing in the above search term shows the results (image to the left). The first result is the Framework reference which lists the Class References found within that framework. You can select this one, but if you want the corelocation class reference (called CLLocation and CLLocationManager) then you’ll need to select one of them on the next page.

When loading up the actual class reference for CLLocation, you will see the overview and tasks as well as what the class inherits from.

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After spending several months learning Objective-C, I still found there were a few things that eluded me. This included things like not fully understanding the different between a view and a view controller on to basics such as how to read and understand the Apple iOS documentation and how to read the different methods when they pop up on auto-complete.

In December 2012 I thankfully came across a book called iOS App Development for Non-Programmers while reading the news on Zite. I had a look at the post, noticed that the book (I thought that there was just 1 at the time) was available to download on the iPad in iBooks. I decided to download a free sample to see what it was all about.

I cannot remember the specifics, but I think the first 4 chapters were available for free. I read them in the first evening within a few hours of downloading the book and thanks to the simple delivery of the content, I finally grasped what a View and View Controller was to the point where I could picture in my mind how they worked and how they were related to each other. I of course knew before what a View did, but understanding the relationship between the two was key for me.

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Updated for Xcode 13.

In this tutorial I will walk you through setting up your first Xcode project so that you can begin working on your first app. If you haven’t installed Xcode yet you can either grab it from the Mac App Store, or if you have an Apple iOS developers account you can download the latest beta version from within there.

Now that you have Xcode installed, it’s time to load it up. Upon loading Xcode you get the following screen:

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I started DevFright towards the end of 2012 with the aim to document what I learn when practicing to code. I started off jumping in to a book called “Objective-C for Dummies” and although the instruction was quite clear, I quickly found that I lacked some understanding of how a few of the basics worked.

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Lecture 3 of CS106A covers the last 3 chapters of Karel the Robot. In particular, it covers stepwise refinement, algorithms as well as gives more details about SuperKarel and what extras he can do. Karel is coming to an end after this lecture, at which point you will move on to specific Java rather than being stuck at Java with the limitations of Karel.

Although all lectures are important to watch and take note, this one provides some good examples of the top-down design approach and how you break a program down/decompose it with stepwise refinement. It’s well worth watching and paying attention to this part. [Read more…]

I briefly mentioned in my post titled What is Top-down Design and Stepwise Refinement? about pre-conditions and post-conditions. In this post I want to explain the two essential points in greater detail.

These two principles are one of the keys to being effective in programming.

What are Pre-conditions?

Lets start with the first of the two which is titled pre-conditions. A pre-condition in its most simple form is a condition that needs to be “true” for a method to be called. This means that the method you are calling is expecting something to be in place before or at the point of the method being called. [Read more…]

Near the beginning of learning Java, you will hear something about top-down design, stepwise refinement and decomposition. This post today will explain what those terms mean as well as provide the reason why you need to tackle programming design with this approach in mind.

Just for the sake of clarity, top-down design is the process of stepwise design and decomposition.

Before you start writing any code for a new program you want to create, you first need to design the program or at least have a specification so that you know exactly what you need to create. [Read more…]