Archives for August 2014

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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Strings are a very common type of variable in many programming languages.  Strings are sequences of characters, used to store text.  Swift in particular works with them in a Unicode-compliant way.  In this post we will discuss some of the higher level aspects of working with Strings in Swift.  The Swift String is very different from its predecessor NSString, but they are bridged together in such a way that you can use a Swift string anywhere you would use an NSString.  You can also use NSString methods on Swift Strings.  In Swift 1.2, NSStrings are not automatically bridged to Swift Strings (but they were beforehand), they must be typecast using the “as” operator.  Swift Strings can still be used where an NSString is expected though, so you only have to typecast an NSString to its Swift equivalent if you still have one.

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