String sclicing make easy

StringSlicingExtesions.swift

extension String {
    public subscript (range: PartialRangeFrom<Int>) -> Substring {
        return self[index(startIndex, offsetBy: range.lowerBound)..<endIndex]
    }
    
    public subscript (range: PartialRangeUpTo<Int>) -> Substring {
        return self[startIndex..<index(endIndex, offsetBy: range.upperBound)]
    }
    
    public subscript (range: PartialRangeThrough<Int>) -> Substring {
        return self[startIndex...index(endIndex, offsetBy: range.upperBound)]
    }
    
    public subscript (range: ClosedRange<Int>) -> Substring {
        return self[index(startIndex, offsetBy: range.lowerBound)...index(startIndex, offsetBy: range.upperBound)]
    }
    
    public subscript (range: Range<Int>) -> Substring {
        return self[index(startIndex, offsetBy: range.lowerBound)..<index(startIndex, offsetBy: range.upperBound)]
    }
}