Cocoa Is My Girlfriend

Just a quick post to point out a great article written by Nick Harris of NewsGator fame. He has looked into the issues with Core Data and encryption.

Core Data and Enterprise iPhone Applications – Protecting Your Data

It has always been a difficult question and fortunately Apple has addressed it for us. Even better, Nick has shared the code so we don’t even need to try and discover the solution ourselves.

Thanks Nick!

So Marcus is the Core Data guy, but I’ve been working with it a good bit myself lately and was recently faced with having to add re-ordering for a list of entities in a UITableView. The methods I found online for accomplishing this all suggested using an NSMutableArray as the data source for the table view. That will work, but I came up with another method, though similar, that achieved what I need without having to switch from using my NSFetchedResultsController as the data source behind the UITableView. In the end, I did use an NSMutableArray, however, I end up using it just to take advantage of its indexing. Read on to see what I mean. Read more

An interesting question came up on Stackoverflow today so I decided to expound upon it in a short blog post.

A situation that I believe we are going to be seeing more and more often is one where application developers are writing multiple “versions” of their applications to be used on the desktop, their iPhone and now the iPad.

Because of that situation, it is becoming even more important that we write as much portable code as possible. Fortunately, our model can be completely portable between the two platforms.

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Everything is moving toward the cloud and unless you’re building calculators, unit converters, or miniature golf score keepers your iPhone app needs to know how to get data from it. In this blog post I intend to demonstrate how to set up a simple server application and how to retrieve data from it and post data to it using Cocoa Touch. I have chosen to use PHP on the server side because of it’s simplicity and ubiquity, and because I’ve know it, somewhat. You should, however, be able to implement something similar using your server side language of choice.

In many cases when you go to access remote data, you do so through a web service API. While services based on such technologies as SOAP or XML-RPC are standards that provide reasonable methods for retrieving and updating data, REST seems to be the methodology gaining the most ground lately. For our purpose in this post I won’t get into great detail of how to implement a REST base web service as, again, REST is not a specific implementation but rather a methodology. (Read up on it elsewhere if you don’t understand what this means). However, I will talk about it briefly so that you can get on the right path for doing your own REST implementation. Read more

Last month I was given the opportunity to write an article for The Pragmatic Programmers great magazine called “PragPub”. I am happy to say that the article I wrote for them was published in this month’s edition. The article, titled “Touching the Core”, is a walk through Apple’s great addition to the Core Data API for the iPhone.

Specifically this article walks through using the NSFetchedResultsController and some best practices in its use. The magazine is available for free on their website, The Pragmatic Bookshelf.

Thanks to the ability to have configurations in a Core Data Managed Object Model and being able to save data to multiple Persistent Stores, it is possible to have a Core Data Model that is constructed from not only an internal model, but from the models of all the plug-ins that are loaded into the application.

In this example we are going to build a basic application with the following requirements:

• A plug-in framework
• Plug-ins can extend the managed object model of the application
• Removal of a plug-in should not corrupt the persistent store.

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In some recent discussions I have been shocked to realize that many developers treat DEBB as gospel. This is a terrible idea. DEBB is written by people like me and I am a moron.

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Every once in a while I find a way to combine multiple technologies that, while they don’t produce anything terribly useful, are very interesting when combined. In this post I will be taking a look at combining Core Animation and QuickTime. As you may or may not be aware, you can draw in a graphics context while your Core Animation animation is running and add each image created to a QTMovie object from QTKit. This enables you to create a QuickTime movie of your Core Animation animation. Here’s how. Read more

iTunes has a very neat way of searching your library, where it takes each word in your search and tries to find that word in multiple fields. For example, you can search for “yesterday beatles” and it will match “yesterday” in the Name field and “beatles” in the Artist field. The basic predicate binding for NSSearchField provided by Interface Builder is not complex enough to archive this kind of search. I need to build the predicate dynamically since I can’t assume what field the user is trying to search and that each additional word should filter the list further – just like iTunes. Here is how to go about adding iTunes-style searching. Read more

A lot of hard work has gone into this book already and I see it becoming the definitive text on the subject of Core Data. The release date is slated for March 30, 2009, but it’s great to see it in beta. If you want to pick up the beta in PDF, it is available now from Pragmatic here: Core Data: Apple’s API for Persisting Data under Mac OS X.

While new Cocoa programmers will find it a great help to getting started quickly with Core Data, the book also covers some really interesting and advanced topics such as data versioning and migration, Spotlight/Quick Look integration, Sync Services, and multi-threading. You can really see Marcus’ command of the subject shine in these chapters which are already available in the beta.

Give Marcus some feedback on the book as it progresses. It’s going to be a great reference for any Cocoa Developer looking to harness the power of Core Data.

$21.00 for the beta PDF $41.35 for the beta PDF plus hard copy when it’s released in March.

Mad props to Marcus. Congratulations!

I’ve been experimenting a great deal lately with OpenGL and QuickTime trying to see how the two technologies work together. It’s been a bit challenging, but fortunately Apple provides two really great resources–number one, sample code. I’ve been able to learn a lot just from the samples they provide in the development tools examples as well as online. And second, the cocoa-dev and quicktime-api lists are great. Lot’s of brilliant people there who are willing to share their knowledge. It’s very helpful, prohibition to discuss the iPhone SDK notwithstanding.

Getting two technologies to work together can be a challenge especially when the bridges between the two are not necessarily clearly laid out in documentation. As I pointed out Apple provides some excellent sample code to help you along, but there is no hand-holding approach to any of it. I actually appreciate that having come from the Windows world as it seems that there all you get sometimes is hand-holding where Microsoft doesn’t trust you, the developer to figure things out and really own what you’re doing. But I digress (wouldn’t be a CIMGF post if I didn’t dig on MS a bit). Read more

Sync Services have come a long way in Leopard. Before Leopard it was an extremely complex operation that was almost completely manual. Needless to say, this sucked and it was probably one of the reasons it was shunned by most developers.

If you are using Core Data in a Leopard application then Sync Services is so trivial that you should be syncing if it makes sense. In this article we are going to cover syncing in a non-Core Data situation as that is quite a bit more complex.

If you have read the Sync Services documentation then you know it is complex. Let me dispel an illusion right away. It is hard. It is not poor documentation, syncing is very hard and very few people get it right. Take a look at Omnifocus to see an example of a company thinking it is easy and losing data. Therefore if you are expecting this subject to be trivial you will be disappointed.

In this example we will be syncing with the bookmarks schema and displaying them in a simple outline view. The outline view itself will be editable and those edits can be synced back. Not terribly useful but provides a very simple example. Read more

In this entry I am going to do something a little different. Instead of showing some wicked code, I am going to reformat one of Apple’s default templates.

Apple writes some amazing code. Unfortunately a lot of their templates demonstrate simply terrible coding practices. What is worse, people take these templates and assume that they are the proper practice for coding in Objective-C and propagate that poor code into their own projects.

The first example I am going to tackle is the AppDelegate class that is auto generated in the Core Data template. This is not the Core Data Document template but the standard application template.

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Undo support in Cocoa is fantastic but for those who have tried to mix it with Core Data know that it can be a bit frustrating. Generally, undo support can be ignored in most applications and it will “just work”. But when Core Data is added to the recipe then things get a bit confusing and more complicated.

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NSDecimalNumber is Objective-C’s solution to numbers that need to be very precise. The documentation defines it as:

NSDecimalNumber, an immutable subclass of NSNumber, provides an object-oriented wrapper for doing base-10 arithmetic. An instance can represent any number that can be expressed as mantissa x 10^exponent where mantissa is a decimal integer up to 38 digits long, and exponent is an integer from –128 through 127.

NSDecimalNumber

If you are dealing with currency at all, then you should be using NSDecimalNumber. However, since it is immutable and definitely not a primitive then it is difficult to use right? Well — yes — a bit. But if you do not want to see your $9.50 item displayed as $9.49999994 or something then you are better off using NSDecimalNumber right from the beginning. Otherwise you are going to be converting to it later and that is a LOT more painful.

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