Sending an email with a loop as body in Swift

I would like to send an email with different steps and values depending on what the user has edited on an image. For that, I'm using UserDefaults to save values.

Then I have the next code into an UIAlertController:

alert.addAction(UIAlertAction(title: "Send", style: .default)
        { action -> Void in
            //i is the last step register

            let nombre = alert.textFields![0]

            for n in 1...self.i {
                print("Step \(n): \(self.filterUserDefaults.string(forKey: "Step_\(n)")!)")
            }

            let filters = [
                "Brillo",
                "Exposicion",
                "Contraste",
                "Saturacion",
                "Saturacion_color",
                "Temperatura",
                "Blanco_Negro",
                "HUE",
                "Tintado_Rojo",
                "Tintado_Rosa",
                "Tintado_Naranja",
                "Tintado_Amarillo",
                "Tintado_Purpura",
                "Tintado_Verde",
                "Tintado_Azul",
                "Tintado_Marron",
                "Tintado_Gris"]
            for filter in filters {
                print("\(filter) = \(self.filterUserDefaults.float(forKey: filter).roundTo(places: 3))")
            }
            self.sendMail(filtro: nombre.text!, body: "XXXX")
        })
        present(alert, animated: true)
    }
    func sendMail(filtro: String, body: String) {
        if MFMailComposeViewController.canSendMail() {
            let mail = MFMailComposeViewController()
            mail.mailComposeDelegate = self
            mail.setToRecipients(["blablabla@gmail.com"])
            mail.setSubject("Filtro \(filtro)")
            mail.setMessageBody(body, isHTML: true)
            present(mail, animated: true)
        } else {
            print("Error presenting email app.")
        }
    }

So printing is working as I expect but the problem is to put these prints into the body of sendMail function...

I tried:

            var steps: [String]?

            for n in 1...self.i {
                steps = ["Step \(n): \(self.filterUserDefaults.string(forKey: "Step_\(n)")!)"]
            }
            .
            .
            .
            self.sendMail(filtro: nombre.text!, body: steps!.joined(separator: "\n"))

But only the last step is written into the body's email and not the array...

Please, can anyone help me?

Thank you in advance!

You are almost there, you need to initialise your array variable and use append

var steps = [String]()

for n in 1...self.i {
    steps.append("Step \(n): \(self.filterUserDefaults.string(forKey: "Step_\(n)")!)")
}
...
self.sendMail(filtro: nombre.text!, body: steps.joined(separator: "\n"))