Classes are a very important part of any Object Oriented language, and Swift is no exception.  When I explain classes to people, I usually think of one to describe a car.  That’s a bit cliché, and done in a WWDC video, so let’s do something different.

Creating A Class in Swift

Let’s say we are making a chat program in Swift.  It primarily sends messages in text format, but occasionally, it will also send images.  We will first create our more general Message class, which we will specialize into those different formats later:

class Message {
    //Message code goes here
}

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The Swift dictionary is another very useful type of collection in Swift.  Like arrays (which you can read more about in my post Arrays and their Methods in Swift), you access them via subscripts usually.  Unlike Swift arrays though, these subscripts accept many more values besides Ints.  There are some limitations, but it nonetheless gives you a lot more capability than arrays if you need they key used to look it up to be something other than a number.  We will also go over some of the methods for dictionaries as well, but there are not nearly as many as for arrays.
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We aren’t done with closures quite yet.  We learned last time about how to write and compress closure expressions in the post Closure Expressions in Swift.  Now, how about we talk about making functions that take them as parameters or return them!  I am still very new to closures, so I do not fully know the power that these hold, so my examples will only show the tip of the iceberg.  When I understand more, I will definitely come back and share, but for the moment, I have to know how to get started with them, so let’s see how that goes.
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Closures are a very useful part of Swift.  An Int is a type that stores an Integer, a String is a type that holds a string.  In the same way, a closure is, basically, a type that holds a function.  With this capability, you can do many things with closures that you couldn’t do in several older languages.  You can assign closures to a variable, you can pass them as arguments to other functions, you can even return one from a function.

Closures in Swift are similar to blocks in Objective-C.  In fact, when you call an Objective-C API from Swift that wants a block, you pass in a closure.  The major difference between them is coding style, and that closure expressions are much easier to read and write in Swift.
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Last time we talked about Arrays in Swift, and the main way to acquire a value was to look it up via an index using subscripts.  Swift made it rather easy to implement subscripts in your own classes.  Sure you can use an Array or Dictionary type if you wanted, and in many cases you should, but if writing it in subscript syntax is clearer and more expressive, that is a good reason to use it.
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