How to implement a regex for password validation in Swift?

You can use Regex for check your password strength

^(?=.*[A-Z].*[A-Z])(?=.*[!@#$&*])(?=.*[0-9].*[0-9])(?=.*[a-z].*[a-z].*[a-z]).{8}$

Regex Explanation : -

^                         Start anchor
(?=.*[A-Z].*[A-Z])        Ensure string has two uppercase letters.
(?=.*[!@#$&*])            Ensure string has one special case letter.
(?=.*[0-9].*[0-9])        Ensure string has two digits.
(?=.*[a-z].*[a-z].*[a-z]) Ensure string has three lowercase letters.
.{8}                      Ensure string is of length 8.
$                         End anchor.

Source - Rublar Link

try with this one for Password must be more than 6 characters, with at least one capital, numeric or special character

^.*(?=.{6,})(?=.*[A-Z])(?=.*[a-zA-Z])(?=.*\\d)|(?=.*[!#$%&? "]).*$

^ assert position at start of the string
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
(?=.{6,}) Positive Lookahead - Assert that the regex below can be matched
.{6,} matches any character (except newline)
Quantifier: {6,} Between 6 and unlimited times, as many times as possible, giving back as needed [greedy]
(?=.*[A-Z]) Positive Lookahead - Assert that the regex below can be matched
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
[A-Z] match a single character present in the list below
A-Z a single character in the range between A and Z (case sensitive)
(?=.*[a-zA-Z]) Positive Lookahead - Assert that the regex below can be matched
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
[a-zA-Z] match a single character present in the list below
a-z a single character in the range between a and z (case sensitive)
A-Z a single character in the range between A and Z (case sensitive)
(?=.*\\d) Positive Lookahead - Assert that the regex below can be matched
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
\d match a digit [0-9]
2nd Alternative: (?=.*[!#$%&? "]).*$
(?=.*[!#$%&? "]) Positive Lookahead - Assert that the regex below can be matched
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
[!#$%&? "] match a single character present in the list below
!#$%&? " a single character in the list !#$%&? " literally (case sensitive)
.* matches any character (except newline)
Quantifier: * Between zero and unlimited times, as many times as possible, giving back as needed [greedy]
$ assert position at end of the string

https://regex101.com/#javascript

more this you can try ....

Minimum 8 characters at least 1 Alphabet and 1 Number:

"^(?=.*[A-Za-z])(?=.*\\d)[A-Za-z\\d]{8,}$"

Minimum 8 characters at least 1 Alphabet, 1 Number and 1 Special Character:

"^(?=.*[A-Za-z])(?=.*\\d)(?=.*[$@$!%*#?&])[A-Za-z\\d$@$!%*#?&]{8,}$"

Minimum 8 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet and 1 Number:

"^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)[a-zA-Z\\d]{8,}$"

Minimum 8 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet, 1 Number and 1 Special Character:

"^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[d$@$!%*?&#])[A-Za-z\\dd$@$!%*?&#]{8,}"

Minimum 8 and Maximum 10 characters at least 1 Uppercase Alphabet, 1 Lowercase Alphabet, 1 Number and 1 Special Character:

"^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[$@$!%*?&#])[A-Za-z\\d$@$!%*?&#]{8,10}"

public func isValidPassword() -> Bool {
    let passwordRegex = "^(?=.*\\d)(?=.*[a-z])(?=.*[A-Z])[0-9a-zA-Z!@#$%^&*()\\-_=+{}|?>.<,:;~`’]{8,}$"
    return NSPredicate(format: "SELF MATCHES %@", passwordRegex).evaluate(with: self)
}

If you need a quick fix. This is validation for a password with regex. Copy/paste in helper or extension file and use it.

func isValidPassword() -> Bool {
    // least one uppercase,
    // least one digit
    // least one lowercase
    // least one symbol
    //  min 8 characters total
    let password = self.trimmingCharacters(in: CharacterSet.whitespaces)
    let passwordRegx = "^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[#?!@$%^&<>*~:`-]).{8,}$"
    let passwordCheck = NSPredicate(format: "SELF MATCHES %@",passwordRegx)
    return passwordCheck.evaluate(with: password)

}

for which missing validation:

func getMissingValidation(str: String) -> [String] {
    var errors: [String] = []
    if(!NSPredicate(format:"SELF MATCHES %@", ".*[A-Z]+.*").evaluate(with: str)){
        errors.append("least one uppercase")
    }
    
    if(!NSPredicate(format:"SELF MATCHES %@", ".*[0-9]+.*").evaluate(with: str)){
        errors.append("least one digit")
    }

    if(!NSPredicate(format:"SELF MATCHES %@", ".*[!&^%$#@()/]+.*").evaluate(with: str)){
        errors.append("least one symbol")
    }
    
    if(!NSPredicate(format:"SELF MATCHES %@", ".*[a-z]+.*").evaluate(with: str)){
        errors.append("least one lowercase")
    }
    
    if(str.count < 8){
        errors.append("min 8 characters total")
    }
    return errors
}

func validpassword(mypassword : String) -> Bool 
    {    

        let passwordreg =  ("(?=.*[A-Z])(?=.*[0-9])(?=.*[a-z])(?=.*[@#$%^&*]).{8,}")
        let passwordtesting = NSPredicate(format: "SELF MATCHES %@", passwordreg)
        return passwordtesting.evaluate(with: mypassword)       
    }

 @IBOutlet weak var password_textfield: UITextField! //create a Password text field IBOutlet

@IBAction func login_btton(_ sender: UIButton) { //Click & Call to Login Button


let password = validpassword(mypassword: password_textfield.text!) //get text Field data & checked through the function


        if(password == false)
        {
             print("Valid Password")  //Use to Alert Msg Box 
        }
        else
        {
             print("Login Safe")     //Use to Alert Msg Box 
        }
    }
## Function Use to validation is password and confirm password is same, Password must have more then some characters , Password contain some special character , Password must one digit , Password must one uppercase letter ##