public func isValidPassword(strPassword : String) -> Bool{
    let charactersetspecialcharacter = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLKMNOPQRSTUVWXYZ0123456789")
    
    if strPassword.rangeOfCharacter(from: charactersetspecialcharacter.inverted) == nil {
        return false
    }
    
    let capitalLetterRegEx  = ".*[A-Z]+.*"
    let textcapitallattertest = NSPredicate(format:"SELF MATCHES %@", capitalLetterRegEx)
    
    let smallLetterRegEx  = ".*[a-z]+.*"
    let textsmalllattertest = NSPredicate(format:"SELF MATCHES %@", smallLetterRegEx)
    
    let numberRegEx  = ".*[0-9]+.*"
    let textnumbertest = NSPredicate(format:"SELF MATCHES %@", numberRegEx)
    
    if !textcapitallattertest.evaluate(with: strPassword) || !textsmalllattertest.evaluate(with: strPassword) || !textnumbertest.evaluate(with: strPassword){
        return false
    }
    return true
}