This is a repost of an answer I wrote on Stack Overflow.
Swift ranges are more complex than NSRange. If you want to try to understand the reasoning behind some of this complexity, read this and this. I'll just show you how to create them and when you might use them.
Closed Ranges: a...b
This range operator creates a Swift range which includes both element a and element b, even if b is the maximum possible value for a type (like Int.max). There are two different types of closed ranges: ClosedRange and CountableClosedRange.
1. ClosedRange
The elements of all ranges in Swift are comparable (ie, they conform to the Comparable protocol). That allows you to access the elements in the range from a collection. Here is an example:
let myRange: ClosedRange = 1...3let myArray = ["a", "b", "c", "d", "e"]
myArray[myRange] // ["b", "c", "d"]
However, a ClosedRange is not countable (ie, it does not conform to the Sequence protocol). That means you can't iterate over the elements with a for loop. For that you need the CountableClosedRange.
2. CountableClosedRange
This is similar to the last one except now the range can also be iterated over.
