MFMailComposeViewController for SwiftUI

MailComposer.swift

import MessageUI
import SwiftUI

struct MailComposer {
    
    struct MessageBody {
        var body: String
        var isHTML: Bool
    }
    
    struct AttachmentData {
        var data: Data
        var mimeType: String
        var fileName: String
    }
    
    var subject: String = ""
    var toRecipients: [String]? = nil
    var ccRecipients: [String]? = nil
    var bccRecipients: [String]? = nil
    var messageBody: MessageBody = .init(body: "", isHTML: false)
    var attachmentData: [AttachmentData] = []
    var preferredSendingEmailAddress: String = ""
    
    var _onFinish: ((MFMailComposeResult, Error?) -> Void)? = nil
    
    func onFinish(perform action: @escaping (MFMailComposeResult, Error?) -> Void) -> Self {
        var modified = self
        modified._onFinish = action
        return modified
    }
}

extension View {
    
    func mailComposer(isPresented: Binding<Bool>, content: () -> MailComposer) -> some View {
        self.modifier(MailComposeViewPresenter(isPresented: isPresented, mailComposer: content()))
    }
}

private struct MailComposeViewPresenter: ViewModifier {
    
    @Binding var isPresented: Bool
    var mailComposer: MailComposer
    
    func body(content: Content) -> some View {
        if MFMailComposeViewController.canSendMail() {
            content
                .sheet(isPresented: $isPresented) {
                    MailComposeView(mailComposer: mailComposer)
                        .edgesIgnoringSafeArea(.all)
                }
        } else {
            content
                .alert(isPresented: $isPresented) {
                    Alert(
                        title: Text("Cannot Send Email"),
                        message: Text("Your device is not configured to send email.")
                    )
                }
        }
    }
}

private struct MailComposeView: UIViewControllerRepresentable {
    
    var mailComposer: MailComposer
    
    @Environment(\.presentationMode) private var presentationMode: Binding<PresentationMode>
    
    func makeCoordinator() -> Coordinator {
        return .init(representable: self)
    }
    
    func makeUIViewController(context: Context) -> UIViewController {
        
        guard MFMailComposeViewController.canSendMail() else {
            assertionFailure("Don't use `MailComposeView` directly and use `mailComposer(isPresented:content:)` instead.")
            presentationMode.wrappedValue.dismiss()
            return UIViewController()
        }
        
        let mailComposeViewController = MFMailComposeViewController()
        mailComposeViewController.mailComposeDelegate = context.coordinator
        
        // After presenting a mail compose view controller, the system ignores any attempts to modify the email using the methods of this class.
        // The user can still edit the content of the email, but your app cannot.
        // Therefore, always configure the fields of your email before presenting the view controller.
        
        mailComposeViewController.setSubject(mailComposer.subject)
        mailComposeViewController.setToRecipients(mailComposer.toRecipients)
        mailComposeViewController.setCcRecipients(mailComposer.ccRecipients)
        mailComposeViewController.setBccRecipients(mailComposer.bccRecipients)
        mailComposeViewController.setMessageBody(mailComposer.messageBody.body, isHTML: mailComposer.messageBody.isHTML)
        mailComposer.attachmentData.forEach { mailComposeViewController.addAttachmentData($0.data, mimeType: $0.mimeType, fileName: $0.fileName) }
        mailComposeViewController.setPreferredSendingEmailAddress(mailComposer.preferredSendingEmailAddress)
        
        return mailComposeViewController
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        context.coordinator.representable = self
    }
    
    class Coordinator: NSObject, MFMailComposeViewControllerDelegate {
        
        var representable: MailComposeView
        
        init(representable: MailComposeView) {
            self.representable = representable
        }
        
        func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
            representable.mailComposer._onFinish?(result, error)
            representable.presentationMode.wrappedValue.dismiss()
        }
    }
}