String extensions

StringExtensions.swift

import Foundation

// MARK: - Getting substrings
// String API lacks take(while:) and suffix(while:) but has drop(while:) and prefix(while:)
extension String {
    func prefix(while predicate: (Unicode.Scalar) -> Bool) -> Substring {
        return self.prefix(while: { (c: Character) -> Bool in
            return c.unicodeScalars.contains(where: predicate)
        })
    }
    
    func drop(while predicate: (Unicode.Scalar) -> Bool) -> Substring {
        return self.drop(while: { (c: Character) -> Bool in
            return c.unicodeScalars.contains(where: predicate)
        })
    }
    
    func take(while predicate: (Unicode.Scalar) -> Bool ) -> Substring {
        return self.prefix(while: predicate)
    }
    
    func suffix(while predicate: (Unicode.Scalar) -> Bool) -> Substring {
       return self.drop(while: predicate)
    }
    
    func split(_ predicate: (Unicode.Scalar) -> Bool) -> (String, String) {
        let left = self.take(while: predicate)
        let right = self.drop(while: predicate)
        return (String(left), String(right))
    }
}

extension String {
  func padding(with padd: Character, length: Int, toLeft: Bool = true) -> String {
    guard self.count < length else {
      return String(self.dropLast(self.count - length))
    }

    let diff = length - self.count
    let paddingString = String(repeating: padd, count: diff)

    return  toLeft ? paddingString + self : self + paddingString
  }
}





// Now this extension can be used like this:

let someString = "Daniel10392"
let (l, r) = someString.split({ CharacterSet.letters.contains($0) })