Swift String Extension

extension String {
    // LEFT
    // Returns the specified number of chars from the left of the string
    // let str = "Hello"
    // print(str.left(3))         // Hel
    func left(_ to: Int) -> String {
        var t = to;
        if (t > self.count) {
            t = self.count;
        } else if (t < 0) {
            t = 0;
        }
        return "\(self[..<self.index(startIndex, offsetBy: t)])"
    }

    // RIGHT
    // Returns the specified number of chars from the right of the string
    // let str = "Hello"
    // print(str.left(3))         // llo
    func right(_ from: Int) -> String {
        var f = from;
        if (f > self.count) {
            f = self.count;
        } else if (f < 0) {
            f = 0;
        }
        return "\(self[self.index(startIndex, offsetBy: self.count-f)...])"
    }

    // MID
    // Returns the specified number of chars from the startpoint of the string
    // let str = "Hello"
    // print(str.left(2, 2))         // ll
    func mid(_ from: Int, _ count: Int = -1) -> String {
        var f = from;
        if (f < 0) {
            f = 0;
        }
        let x = "\(self[self.index(startIndex, offsetBy: f)...])"
        return x.left(count == -1 ? x.count : count)
    }

    // MIDAFTER
    // Returns the substring that are found after the specified search string
    // let str = "Hello"
    // print(str.midAfter("e"))       // llo
    func midAfter(_ search : String, _ count: Int = -1) -> String {
        let r = self.range(of: search);
        if (r == nil) {
            return "";
        }
        let lb = r!.lowerBound;
        let x = "\(self[lb...])".mid(1);
        return x.left(count == -1 ? x.count : count)
    }
}