// ---------------------------------------------------------
// with VC - run in Playground, Simulator, Device
// ---------------------------------------------------------

class RXViewController : UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let strs: [String] = [
            "abcd",
            "abcdabcd",
            "abcdAbcd",
            "abcd1bcd",
        ]

        strs.forEach { s in
            print(s, validatePassword(password: s))
        }

    }

    private func validatePassword(password : String) -> Bool {
        return password.regexMatches(regex: #"^(((?=.*[a-z]{1})(?=.*[A-Z]{1}))|((?=.*\d{1})(?=.*[a-zA-Z]{1}))|((?=.*\W{1})(?=.*[a-zA-Z]{1}))|((?=.*\d{1})(?=.*\W{1}))).{8,20}$"#)
    }

}

public extension String {
    func regexMatches(regex : String) -> Bool {
        let predicate = NSPredicate(format: "SELF MATCHES %@", regex)
        return predicate.evaluate(with: self)
    }
}

// ---------------------------------------------------------
// playground without VC
// ---------------------------------------------------------

import Foundation

let strs: [String] = [
    "abcd",
    "abcdabcd",
    "abcdAbcd",
    "abcd1bcd",
]

strs.forEach { s in
    print(s, validatePassword(password: s))
}

private func validatePassword(password : String) -> Bool {
    return password.regexMatches(regex: #"^(((?=.*[a-z]{1})(?=.*[A-Z]{1}))|((?=.*\d{1})(?=.*[a-zA-Z]{1}))|((?=.*\W{1})(?=.*[a-zA-Z]{1}))|((?=.*\d{1})(?=.*\W{1}))).{8,20}$"#)
}

public extension String {
    func regexMatches(regex : String) -> Bool {
        let predicate = NSPredicate(format: "SELF MATCHES %@", regex)
        return predicate.evaluate(with: self)
    }
}

// ---------------------------------------------------------------------
// output is the same with VC in Playground, Simulator, Device
// as well as Playground Without VC

// abcd false
// abcdabcd false
// abcdAbcd true
// abcd1bcd true