An excerpt of key functional from https://gist.github.com/zethraeus/34d2aa882c106d8f44ecda6a976361db#file-badonboardingmanager-swift

BadOnboardingManagerExcerpt.swift

private func validatePassword() {
    self.passwordIsValid = false
    self.passwordIssue = nil

    guard let username = self.username,
          let email = self.email,
          let phoneNumber = self.phoneNumber,
          let password = self.password
    else {
        return
    }

    if password.count < 10 {
        self.passwordIssue = .tooShort
    }
    if password.contains(username) {
        self.passwordIssue = .containsUsername
    }
    if password.contains(email) {
        self.passwordIssue = .containsEmail
    }
    if password.contains(phoneNumber) {
        self.passwordIssue = .containsPhoneNumber
    }
    if !passwordContainsAtLeastOneNumber() {
        self.passwordIssue = .noNumbers
    }
    if !passwordContainsAtLeastOneSpecialCharacter() {
        self.passwordIssue = .noSpecialCharacters
    }
    self.passwordIsValid = true
}