Archives for March 2014

Much like Casey Liss of the Accidental Tech Podcast, talked about recently on the Debug podcast, I came from C# before I started working on Objective-C.  One frustration he had originally with Objective-C was with getting a human readable date out of an NSDate object, when it was so easy to just type someDateTime.toString() in C#.  That was also one of my earliest frustrations, and I thought it would be nice to share with my readers.

In C#, you store dates in objects of the type DateTime.  The Objective-C equivalent of this is NSDate.  In C#, you can simply create a specific date date with:

DateTime someDate = new DateTime(2013, 12, 31);

And that would make a DateTime object for December 31, 2013.  There are a few ways to do this in Objective-C, and while they are not as easy, they do make it much more friendly to using non-Gregorian calendar systems.  NSDateFormatter can both format an NSDate into a string (more on this later), but it can also attempt to parse a string with date data.  The more exact way though, would probably be to use NSDateComponents.

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In my previous articles, you’ve probably seen properties used many times. In this article I wanted to write down (in one place) and explain the attributes that can be used on them. At least in this context, “attributes” refers to the modifiers to the property (usually strong and nonatomic in my previous articles). I have covered those two a little bit in a previous article, but I wanted to list them all here.

 Valid Property Attributes

• atomic
• nonatomic
• strong
• weak
• readwrite
• readonly
• getter=
• setter=
• copy
• assign
• retain
• unsafe_unretained

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Have you ever wished you could add a method to an existing class that you don’t have the code for?

Well, now you can, with categories.

Categories let you extend an existing class with whatever method you deem fit.  It is pretty useful to add helper methods to other classes that help parse the date in a way the class make perhaps did not intend.  You can also use it to split up your own classes so that if you have some big omni-class that does several things, you can opt in to just the parts you want by only including those categories.

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