How to create range in Swift?

Question

In Objective-c we create range by using NSRange

NSRange range;

So how to create range in Swift?

Answer 1

I find it surprising that, even in Swift 4, there's still no simple native way to express a String range using Int. The only String methods that let you supply an Int as a way of obtaining a substring by range are prefix and suffix.

It is useful to have on hand some conversion utilities, so that we can talk like NSRange when speaking to a String. Here's a utility that takes a location and length, just like NSRange, and returns a Range<String.Index>:

func range(_ start:Int, _ length:Int) -> Range<String.Index> {
    let i = self.index(start >= 0 ? self.startIndex : self.endIndex,
        offsetBy: start)
    let j = self.index(i, offsetBy: length)
    return i..<j
}

For example, "hello".range(0,1)" is the Range<String.Index> embracing the first character of "hello". As a bonus, I've allowed negative locations: "hello".range(-1,1)" is the Range<String.Index> embracing the last character of "hello".

It is useful also to convert a Range<String.Index> to an NSRange, for those moments when you have to talk to Cocoa (for example, in dealing with NSAttributedString attribute ranges). Swift 4 provides a native way to do that:

let nsrange = NSRange(range, in:s) // where s is the string

We can thus write another utility where we go directly from a String location and length to an NSRange:

extension String {
    func nsRange(_ start:Int, _ length:Int) -> NSRange {
        return NSRange(self.range(start,length), in:self)
    }
}

Answer 2

Xcode 8 beta 2 • Swift 3

let myString = "Hello World"
let myRange = myString.startIndex..<myString.index(myString.startIndex, offsetBy: 5)
let mySubString = myString.substring(with: myRange)   // Hello

---

Xcode 7 • Swift 2.0

let myString = "Hello World"
let myRange = Range<String.Index>(start: myString.startIndex, end: myString.startIndex.advancedBy(5))

let mySubString = myString.substringWithRange(myRange)   // Hello

or simply

let myString = "Hello World"
let myRange = myString.startIndex..<myString.startIndex.advancedBy(5)
let mySubString = myString.substringWithRange(myRange)   // Hello

Answer 3

You can use like this

let nsRange = NSRange(location: someInt, length: someInt)

as in

let myNSString = bigTOTPCode as NSString //12345678
let firstDigit = myNSString.substringWithRange(NSRange(location: 0, length: 1)) //1
let secondDigit = myNSString.substringWithRange(NSRange(location: 1, length: 1)) //2
let thirdDigit = myNSString.substringWithRange(NSRange(location: 2, length: 4)) //3456

Answer 4

(1..<10)

returns...

Range = 1..<10