The iOS Dev Diary

In this episode I’ll show you how to build a UICollectionView from scratch in Xcode 6. The class is available for both iPhone and iPad since iOS 6. If you know how to build a UITableView then building a UICollectionView will be familiar to you.

I’ll start with a single view application, delete the ViewController class and start fresh with a UICollectionViewController. Next I’ll add a custom class for the UICollectionViewController and UICollectionViewCell and then we’ll hook it up in the storyboard.

By the end we’ll have a simple Collection View App which allows multiple selections. I’m going to use this project to build on with other features in the future.

The template provides a few good starting points, but they need to be changed to work. First there’s the cell’s reuse identifier, conveniently added as a static at the top of the implementation file. It’s there so we only need to change this once in the file. Replace it with your own, and remember to make the same change in the storyboard:

Next up is the viewDidLoad method. To make dequeuing cells easier, Apple have provided a registerClass method. If you don’t add your custom cell here, nothing will appear when you run the app. I found that simply commenting out the line works just as well.

The reason they provide this is so that the dequeueCellWithIdendifier method knows which custom cell class to instantiate (prior to iOS 6 it returned nil, but that check is no longer necessary).

I’m also adding multiple selections here, something that cannot be done in the storyboard.

Much like with UITableViews, we need to provide the number of sections, as well as the number of items in each section:

If you don’t provide the sections method, it is assumed that you have one section. Usually we’d have some data and would return a count of how many items we have rather than fixed values here.

We also need to provide what’s in each cell. Here we can add data to labels, populate UIImageViews and many other things our collection view cells may need:

With UITableViews there were four styles of table cells we could choose from out of the box. A collection view cell on the other hand is completely blank, and we’re expected to provide everything inside it. This means we need a custom UICollectionViewCell class for our project.

Anything we drag into the prototype cell in the storyboard can be hooked up to that custom class and the configured in the above cellForItemAtIndexPath method. Make sure any outlets are defined in the cell’s header file.

Collection view cells have several views layered on top of each other. At the bottom is the backgroundView and the selectedBackgroundView. These are not configured by default, but if we add our own views here, the cell knows how display selections.

Above the background/selectedBackgroundView is the contentView, and on top of the contentView is where we can add out own outlets (like labels and images). If we leave the contentView’s background colour transparent, the views underneath will be visible, and hence selections are visible too.

Here’s how to configure our custom cell with two colours for selection and deselection. I’m doing this in awakeFromNib, which is called as soon as our cell is instantiated:

The code I’m writing here is available as a demo project on GitHub:

The Unwind Segue was introduced in iOS 6 to make retrieving data from a dismissed view controller easier. A regular Segue allows us to send data from one view controller to another, but it’s not easy to bring data back if the user has changed or added details in that view controller. That’s where an software like the one at Paxata comes in.

Here’s how to create one. I’m assuming we have two view controllers at our disposal, ViewController1 has initiated a standard segue, maybe passing some data. The user then changes the data, and upon saving the data, ViewController2 is dismissed and we’re going back to ViewController1.

So in ViewController1 we’ll add a method we can use as an Unwind Segue, which we later hook up in the storyboard to the Exit object. Here’s that method:

It doesn’t matter what the method is called, just as long as it resides in ViewController1, in which you’ve imported the ViewController2.h file. What DOES matter however that our method is an IBAction and takes a UIStoryboardSegue as a parameter – otherwise Interface builder won’t recognise it, and you won’t be able to drag to the Exit object later.

Meanwhile, in ViewController2, we can make use of the following method which is often provided as a stub in new view controller classes:

prepareForSegue is called just before the unwind segue (or any segue for that matter) is about to begin. You may want to read out a text field or any other values and add it to the object or variable that ViewController1 needs access to.

With our code in place, control-drag from the button you’d like to use for initiating the segue. You can hook up multiple buttons to the same unwind segue.

Control-drag each button to the Exit object (in ViewController2):

As soon as the button is pressed, the unwind code in ViewController1 is executed and ViewController2 is dismissed.

I’ve put together a quick demo project on GitHub which is the code I’m creating the screencast above:

In this episode core data I’ll talk you through the lingo of Core Data: those scary classes and expressions that you’ll frequently come across. In fact, this is the start of a new series:

Core Data Nuggets are bite-sized chunks about the framework. Dip in and out or watch them all in a row and learn how this super complicated framework works and what it has to offer.

Don’t get overwhelmed by Core Data: it wants to help – it’s just not designed with humans in mind.

As always, enjoy!

And finally in the last part I’ll show you how to restore purchases.

Note that you must implement a restore option for non-consumable products or the review team will reject your app.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

In this part we’ll see our hard work comes to life on a real device while we’re performing our purchase in the App Store Sandbox.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

Learn how to make the purchase in this part of our series about in-app purchases.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

In this part we’ll setup the observers needed to react to responses from the App Store.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

In this part I’ll talk you through building a custom shop class and how to make “first contact” with the App Store.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

In this 7-part screencast series I’ll show you how to create an In-App Purchase in iOS 7 with Xcode 5.1.

The course will run you through everything from setting up your product in iTunes Connect, creating a custom shop class for easy re-use, making “first contact” with the App Store and how to deal with its responses. I’ll explain the overall concept in Part 1.

I’ll describe the overall concept in this part, and how to setup your your app for use with In-App purchases. We’ll setup a new App ID in Member Center and then create a product in iTunes Connect.

You can download the full source code of what I’m building in this screencast on GitHub:

I’m following my earlier two articles almost to the letter, here they are for reference:

In this series I’ll show you how to create Popovers on iPad. They’re fairly easy to create once you get the hang of the inner workings of the UIPopoverController.

I’ll show you how to create basic Popover in code and in your Storyboard, and we’ll discuss how you can retrieve data from a Popover when it’s dismissed. We’ll do this with a simple UIDatePicker. In the last video I’ll demonstrate how you can pick images from the camera roll using the UImagePickerController with a Popover – which is how you’re meant to do it on iPad.

The series contains three videos in total:

Enjoy!