Sending a contact us email on iOS 14 (can be also used with SwiftUI)

MailComposeViewController.swift

//
//  Feel free to use this code in your project.
//  Inspired by SO answer https://stackoverflow.com/a/65743126
//  Uses DeviceKit as a dependency https://github.com/devicekit/DeviceKit
//

import Foundation
import MessageUI
import DeviceKit

class MailComposeViewController: UIViewController, MFMailComposeViewControllerDelegate {

    static let shared = MailComposeViewController()

    func sendContactUsEmail() {
        let email = Constants.Email.contactEmailAddress
        let subject = Constants.Email.contactEmailSubject
        let body = String(
            format: Constants.Email.body,
            Device.current.description,
            Device.current.systemVersion?.description ?? "Unknown",
            UIApplication.appVersion ?? "Unknown")

        if MFMailComposeViewController.canSendMail() {
            sendWithMailApp(email: email, subject: subject, body: body)
        } else {
            sendWith3rdPartyEmailClient(email: email, subject: subject, body: body)
        }
    }
    
    // MARK: - MFMailComposeViewControllerDelegate

    func mailComposeController(
        _ controller: MFMailComposeViewController,
        didFinishWith result: MFMailComposeResult,
        error: Error?
    ) {
        controller.dismiss(animated: true, completion: nil)
    }
    
    // MARK: - Private funcs
    
    private func sendWithMailApp(email: String, subject: String, body: String) {
        let mail = MFMailComposeViewController()
        mail.mailComposeDelegate = self
        mail.setToRecipients([email])
        mail.setSubject(subject)
        let encodedBody = body.replacingOccurrences(of: "/n", with: "<br>")
        mail.setMessageBody(encodedBody, isHTML: true)
        UIApplication.shared.windows.last?.rootViewController?.present(mail, animated: true, completion: nil)
    }

    private func sendWith3rdPartyEmailClient(email: String, subject: String, body: String) {
        guard
            let encodedParams = "subject=\(subject)&body=\(body)"
                .addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)?
                .replacingOccurrences(of: "/n", with: "%0D%0A")
        else { return }

        let urlString = "mailto:\(email)?\(encodedParams)"

        guard
            let url = URL(string: urlString)
        else { return }

        UIApplication.shared.open(url)
    }
}

enum Constants {

    struct Email {
        static let contactEmailAddress = "[email protected]"
        static let contactEmailSubject = "App feedback"
        static let body = "/n/n——Important debug data——/nDevice: %@ /niOS: %@ /nApp version: %@/n———————————————"
    }
}

extension UIApplication {

    static var appVersion: String? {
        return Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String
    }
}