Thousandapologies

In april werd ik door de website leraar24.nl geïnterviewd over het laatste experiment van mijn promotieonderzoek. Hieronder is het videoverslag van dit interview en het experiment te vinden. Erg leuk geworden vind ik zelf

I must say I really love developing for the iPhone; never seen such a complete and helpful API as the one offered by Apple. Also XCode is just brilliant. However, one thing that can be a complete nightmare is code signing. Especially, when developing on the simulator, one doesn’t encounter the specific errors that can stop you from deploying your app to a real device. One such error I encountered already before, but completely forgot about. When trying to deploy my language learning software on a 3G device I suddenly was confronted by a weird error “object file format invalid or unsuitable”, my first suspicions were the JSON framework I recently added. These suspicions turned out to be correct; after finding this helpful blogpost I was finally able to solve the problem. A short recap of what I did:

1. Right click the Target you’re building in my case “Language Learning”, and click on “Get Info”
2. Go to the build tab
3. Find the Code Signing section
4. Add the $(SDKROOT)/ResourceRules.plist to the “Code Signing Resource Rules Path” in this section
5. Clean the build (Build Menu/Clean)
6. Rebuild your app and you should be good to go again

I would like to share with you a problem that has been a proverbial pain in the bum for me and has been nagging me for quite some time. As an application developer the last thing you want to have is people waiting for your application without showing them some kind of progress. For my work, I’m currently developing an iPhone application for the MACE portal that allows users to access content, more specifically images, related to a building in their vicinity. For each building, the images available are shown in a grid view. Thus, this involves a lot of thumbnail images to be downloaded from a webpage and thus can lead to some lags in the software. To give the users some feeling of progress I decided I wanted to load the thumbnails and show them in the UI as soon as they were download. While it sounded like a trivial problem, it took me quite some time to solve and by sharing it I hope to save you all some time. Shortly the problem can be broken down in a couple of steps:

1. Creating a method to update the UI from the main thread
2. Setting up a thread to download thumbnail images in the background & sending updates to NSNotificationCenter from this thread
3. Creating a method to receive notification updates and registering this method with NSNotificationCenter

Below I will provide some examples on how to solve these problems and provide you with the necessary code. Most of it, I already figured out for my self, but the final step to get it working was given by this post.

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