Ever wonder what various apps like Photos or Safari use when you click on the share button? So did I until a few days ago. It is apparently UIActivityViewController. I just learned a bit about how to use it, so I thought I would pass it along.

Update November 10, 2014:  Want to see how to use UIActivityViewController in Swift?  Check out the my newer post Add sharing to your Swift app via UIActivityViewController [Read more…]

Have you ever wanted to have your app give a notification when it is not open, but don’t have a web backend?  That’s where UILocalNotification comes in.

One caveat, UILocalNotification cannot open your app (at least as far as I know), so it can only run at pre-programmed times, but that is still useful in many situations.

An example use of UILocalNotification

UILocalNotification is pretty simple to setup in the simplest cases.  Below is an example of one I used:
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For an app I am working on, I wanted to use some specific colors outside of the standard system ones.  Using UIColor is pretty easy, but I thought I would share with you how to use it in its simplest form, and a help category I made to make working with the built in functions a bit easier, and a tool I JUST found while working on this post that would have been very nice last week.  If you want to learn how to make a category, see my previous post Objective-C Categories.

Creating a UIColor Object

UIColor has several methods to generate a color based off of components.  The available ones are:

• colorWithWhite:alpha:
• colorWithHue:Saturation:brightness:alpha:
• colorWithRed:green:blue:alpha:
• colorWithCGColor:
• colorWithPatternImage:
• colorWithCIColor:

But we are going to work with colorWithRed:green:blue:alpha: in this post.

Also, each of those has an init form (so colorWithRed:green:blue:alpha: is initWithRed:green:blue:alpha: ).  This makes less difference in a post ARC world, but for reference, the initWith forms give your class ownership of the object, and so it must be released when you are done with it to avoid memory leaks.  The colorWith form (also called a “Factory Method”), does not give your class ownership, so it does not need to be released by your class, that is handled by the system.  Since ARC automatically counts your references, they are effectively the same for the programmer nowadays.

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I have mentioned NSString in previous posts, so I might as well write about it in my new set of class reference posts.  I also keep forgetting the formatting specifiers, and so I’ll put up a table of those for everyone to see when you want to know the correct specifier for a formatted string.  As we’ve seen before, an NSString is an object that represents a block of text.  The name presumably comes from the fact that it is a string of characters, though that is just supposition, but does make it slightly easier to remember.  For a little history, in C, a string was an array of an 8-bit variable named “char”, which was short for character.  In each of those spots of an array was a number that would denote a letter based off of the ASCII standard.  If you’re curious, here is a link to a copy of the ASCII Table.  At the end of the string, to denote the end, was a NUL character, which is denoted by the number 0.  Unlike most of my trips into history though, this is actually still quite relevant to Objective-C.

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Have you had a collection of objects that you want to by name?  Lets say you had an object that contains contact info for a person.  If I wanted to see the contact information for somebody, I’d want to just tell something, “Hey, give me Jimmy’s contact info”, and it would get it for me.  That is exactly what NSDictionary does for you.

NSDictionary is way to perform easy lookups for objects stored in the dictionary, via a key of some sort.  It basically stores data in something called a “key value pair”.  I will use the even simpler example of looking up the definition of a word in a standard Miriam-Webster style dictionary.  The word you are looking up is the “key.”  The definition you are trying to find for that word is the “value.”  In this post, I’ll go over some of the basics.

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