Adding truncation to Swift Strings

StringTruncationExtension.swift

import Foundation

extension String {

    func truncateEnd(length: Int, omissionMarker: String? = "...") -> String {
        guard self.characters.count > length  else { return self }

        return self.substringToIndex(self.startIndex.advancedBy(length)) + (omissionMarker ?? "")
    }

    func truncateMiddle(length: Int, omissionMarker: String? = "...") -> String {
        guard self.characters.count > length  else { return self }

        let start = self.truncateEnd(length / 2, omissionMarker: nil)
        let end = self.truncateBeginning(length / 2, omissionMarker: nil)

        return start  + (omissionMarker ?? "") + end
    }

    func truncateBeginning(length: Int, omissionMarker: String? = "...") -> String {
        guard self.characters.count > length  else { return self }

        return (omissionMarker ?? "") + self.substringWithRange(self.endIndex.advancedBy(-length)..<self.endIndex)
    }
}