Extract closure

private func performLogin() {
    let email = self.textFieldEmail.text ?? ""

    let isEmailValid = self.emailValidator.isEmailValid(email: email)
    // To be extracted
    textFieldEmail.textColor = isEmailValid ? UIColor.black : UIColor.red

}

private func performLogin() {
    let email = self.textFieldEmail.text ?? ""

    let isEmailValid = self.emailValidator.isEmailValid(email: email)
    // Extracted closure
    let setFiledStyle = { (isEmailValid: Bool) in
        self.textFieldEmail.textColor = isEmailValid ? UIColor.black : UIColor.red
    }
    setFiledStyle(isEmailValid)

}