String, substring, Range, NSRange in Swift 4

Question

I am using the following code to get a String substring from an NSRange:

func substring(with nsrange: NSRange) -> String? {
             


        

Answer 1

With Swift 4 we can get substrings this way.

1. Substring from index

   let originStr = "Test"
   let offset = 1
   let str = String(originStr.suffix(from: String.Index.init(encodedOffset: offset)))
   

2. Substring to index

   let originStr = "Test"
   let offset = 1
   String(self.prefix(index))
   

Answer 2

Use Range(_, in:) to convert an NSRange to a Range in Swift 4.

extension String {
    func substring(with nsrange: NSRange) -> Substring? {
        guard let range = Range(nsrange, in: self) else { return nil }
        return self[range]
    }
}