String truncate extension for Swift 4

string-truncate.swift

extension String {
  /*
   Truncates the string to the specified length number of characters and appends an optional trailing string if longer.
   - Parameter length: Desired maximum lengths of a string
   - Parameter trailing: A 'String' that will be appended after the truncation.
    
   - Returns: 'String' object. 
  */
  func trunc(length: Int, trailing: String = "…") -> String {
    return (self.count > length) ? self.prefix(length) + trailing : self
  }
}

// Swift 4.0 Example
let str = "I might be just a little bit too long".truncate(10) // "I might be…"

Thank you!