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// ---------------------------------------------------------
// 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