Author Archives: Gregor Berginc

Snapshots in Xcode 4

I (now) know this feature has been in Xcode for years but I just discovered it. Snapshots in Xcode 4 provide fast and reliable mechanism to make safe copies of your projects.

To create a snapshot simply choose File > Create Snapshot… choose a name and optional description and you are ready to make major changes to your project! To restore to a snapshot go to the Organizer window (Window > Organizer) and browse for the desired snapshot on the Projects tab. Click Restore Snapshot at the bottom and your project is exactly the same state as it was when you created the snapshot!

Just great!


Extending classes with categories in Objective-C

For the last couple of months I’ve been playing around with cocos2d to build a simple catch ’em all game for kids to learn the alphabet, numbers etc. It is progressing great so I am planning to release the first preview soon. For the time being, my son is the only tester.

Cocos2d is a great open-source 2d (and 3d) game engine with support for many advanced features that every game is comprised of. However, in this post I will only concentrate on actions. During one of the refactoring, I realised that I frequently need to execute a specific action after all other actions have be successfully executed. Cocos2d supports this via special actions like CCCallFunc and CCCallBlock. For this to work, you need to encapsulate your action in a CCSequence and add a CCCallBlock at the end. For example, if you need to perform an action after the FadeTo action is completed, you need something like this (alpha is an instance of CCSprite which in turn is a subclass of CCNode):

[alpha runAction:[CCSequence actions:

[CCFadeTo actionWithDuration:2.0f opacity:50],

[CCCallBlock actionWithBlock:animCompletionBlock],


As there is much of a boilerplate code in the above example, I decided to extend the CCNode to behave much like UIView animations do, i.e., by using a special block invoked after actions are finished. However, instead of extending the CCNode class in the source code, I extended it using Objective-C feature called categories. Categories allow developers to extend a class (not subclass!) in a way that does not affect the original implementation. Here is an example of an interface with a special category Helper (as in helper methods):

@interface CCNode (Helper)

– (CCAction*) runAction:(CCFiniteTimeAction *)action completion:(void(^)())block;


The implementation is trivial and resembles the example above:

@implementation CCNode (Helper)

– (CCAction*) runAction:(CCFiniteTimeAction *)action completion:(void(^)())block


CCSequence *sequence = [CCSequence actions:action,

[CCCallBlock actionWithBlock:block],


return [self runAction:sequence];



Now the above example can be rewritten as a single line of code:

[alpha runAction:[CCFadeIn actionWithDuration:2.0f] completion:animCompletionBlock];

Much cleaner and easier to invoke a block after the action is finished. Surely, the same extension mechanism could be used for other block methods that also pass the node and user data object to the block.

Resizing views in the Interface Builder

For the last couple of days I’ve been trying to change the size of some of my views in the Interface Builder (v3.2.5). Well, not the whole time, of course. 😉

Although I followed some of the tutorials that successfully changed the size, I was not able to change it. No matter how I created the view. Corresponding fields in the “View size” tab (Inspector window) were disabled, read-only.

I then noticed that the “Status Bar” property was set to “Gray” in the View Attributes. After I changed the value to “Unspecified” both fields became enabled and I could then change the height of my view. The same happens when you have any of the other two bars set to anything else but “Unspecified”, namely the “Top Bar” and the “Bottom Bar”.

Hello 3Dimenzija

This is the first blog post ever made on the WordPress platform. I wish you will find a lot of interesting stuff here in the near feature posts.