Native Objective-C calls from cpp/qt (IOS Email-call)

[J.Hilk]

Hello everyone,

I'm trying send E-Mails with attachments that are created by my application. Because this is only really possible with native IOS/Objective-C code, I created the following simple (pure x-code) example that upon a button press shows the Mail-App:

- (IBAction)showEmail :(id)sender{
    //Email Subject
    NSString *emailTitle = @"Test Email";
    
    //Email Content
    NSString *messageBody = @"ios programming is so fun!";
    
    //To Address
    NSArray *toRecipents = [NSArray arrayWithObject:@"support@myCompany.com"];
    
    MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
    mc.mailComposeDelegate = self;
    
    [mc setSubject:emailTitle];
    [mc setMessageBody:messageBody isHTML:false];
    [mc setToRecipients:toRecipents];
    
    [self presentViewController:mc animated:YES completion:NULL];
}

- (void) mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(nullable NSError *)error{
    switch (result) {
        case MFMailComposeResultCancelled:
            NSLog(@"Mail cancelled");
            break;
        case MFMailComposeResultSaved:
            NSLog(@"Mail saved");break;
        case MFMailComposeResultSent:
            NSLog(@"Mail sent");break;
        case MFMailComposeResultFailed:
            NSLog(@"Mail sent failure: %@", [error localizedDescription]);
            break;
        default:
            break;
    }
    
    [self dismissViewControllerAnimated:YES completion:NULL];
}

this works fine, EMail window appears and sends the E-Mail away without problem.

To intereate this now in cpp/Qt, U create a native c-interface:

//ObjectiveCInterface.h
#ifndef __OBJECTIVECINTERFACE_H__
#define __OBJECTIVECINTERFACE_H__

class MyClassImpl
{
public:
    MyClassImpl (void);
    ~MyClassImpl (void);

    void init (void);

    void showEmail(char * aCstr);

private:
    void * self;
};

#endif

and a cpp/objective c - combi class

//MyObject.h
#import "ObjectCInterface.h"
#import <Foundation/Foundation.h>

@interface MyObject : NSObject
{

}

- (void)showEmail:(char *) aCStr;

@end

//MyObject.mm
#import "MyObject.h"
#import <UIKit/UIKit.h>
#import <MessageUI/MessageUI.h>

@implementation MyObject

MyClassImpl::MyClassImpl( void ) : self(NULL){
    init();
}

MyClassImpl::~MyClassImpl( void ){
    [(id)self dealloc];
}

void MyClassImpl::init( void ){
    self = [ [MyObject alloc] init];
}


void MyClassImpl::showEmail(char *aCstr){
    NSLog(@"logMyMessage");
    [(id)self showEmailPopup:aCstr];
}


- (void) showEmailPopup:(char *)aCStr{
    NSLog(@"LogMyMessage in Obj");
    NSLog([NSString stringWithUTF8String:aCStr]);

/* Code From working X-Code Project
    //Email Subject
    NSString *emailTitle = @"Test Email";
    
    //Email Content
    NSString *messageBody = @"ios programming is so fun!";
    
    //To Address
    NSArray *toRecipents = [NSArray arrayWithObject:@"support@myCompany.com"];
    
    MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
    mc.mailComposeDelegate = self;
    
    [mc setSubject:emailTitle];
    [mc setMessageBody:messageBody isHTML:false];
    [mc setToRecipients:toRecipents];
    
    [self presentViewController:mc animated:YES completion:NULL];
*/
}

@end

//Mainwindow
#include "mainwindow.h"
#include "ui_mainwindow.h"

#include "ObjectCInterface.h"

#include <QPushButton>
#include <QVBoxLayout>
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow), _impl( NULL )
{
    ui->setupUi(this);

    QPushButton *btn = new QPushButton("Email");
    connect(btn, &QPushButton::clicked, this, &MainWindow::btnClicked);
    QVBoxLayout *lay = new QVBoxLayout(ui->centralWidget);
    lay->addWidget(btn);

    init();
}

void MainWindow::btnClicked(){
    qDebug() << "BtbClicked";
    showNativeEmail();
}

MainWindow::~MainWindow()
{
    if(_impl)
    {
        delete _impl;
        _impl = NULL;
    }
    delete ui;
}

void MainWindow::init()
{
    _impl = new MyClassImpl();
}

void MainWindow::showNativeEmail()
{    
    _impl->showEmail((char*)("Path/to/Attachment.pdf"));
}

So far so good, when I press the Button in my QMainWindow I do get the NSLog entry "Path/To/Attachment.pdf"

But when I now copy and paste the working code from the X-Code Project into my MyObject.mm class I do get a couple of warnings and when I run the program I get a sigbart-crash.
in the Line

[self presentViewController:mc animated:YES completion:NULL];

Clearly I'm missing something. Anyone got an Idea what it could be ?

[J.Hilk]

Never mind, @SGaist , I managed to make it work.

//ObjectCInterface.h
#ifndef __OBJECTIVECINTERFACE_H__
#define __OBJECTIVECINTERFACE_H__

class MyClassImpl
{
public:
    MyClassImpl (void);
    ~MyClassImpl (void);

    void init (void);

    void showEmail(char * aCstr);

private:
    void * self;
};

#endif

//MyObject.h
#import "ObjectCInterface.h"
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <MessageUI/MessageUI.h>

@interface MyObject : UIViewController  <MFMailComposeViewControllerDelegate>
{

}

- (void)showEmailPopup:(char *) aCStr;

@end

//MyObject.mm
#import "MyObject.h"

@implementation MyObject


MyClassImpl::MyClassImpl( void ) : self(NULL){
    init();
}

MyClassImpl::~MyClassImpl( void ){
    [(id)self dealloc];
}

void MyClassImpl::init( void ){
    self = [ [MyObject alloc] init];
}


void MyClassImpl::showEmail(char *aCstr){
    NSLog(@"logMyMessage");
    [(id)self showEmailPopup:aCstr];
}


- (void) showEmailPopup:(char *)aCStr{
    NSLog(@"LogMyMessage in Obj");
    NSLog([NSString stringWithUTF8String:aCStr]);

    //Email Subject
    NSString *emailTitle = @"Test Email";
    
    //Email Content
    NSString *messageBody = @"ios programming is so fun!";
    
    //To Address
    NSArray *toRecipents = [NSArray arrayWithObject:@"support@MyCompany.com"];
    
    MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
    mc.mailComposeDelegate = self;
    
    [mc setSubject:emailTitle];
    [mc setMessageBody:messageBody isHTML:false];
    [mc setToRecipients:toRecipents];
    
    UIViewController * topController = [UIApplication sharedApplication].keyWindow.rootViewController;
    while (topController.presentedViewController){
        topController = topController.presentedViewController;
    }
    
    [topController presentViewController:mc animated:YES completion:NULL];
}


- (void) mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(nullable NSError *)error{
    switch (result) {
        case MFMailComposeResultCancelled:
            NSLog(@"Mail cancelled");
            break;
        case MFMailComposeResultSaved:
            NSLog(@"Mail saved");break;
        case MFMailComposeResultSent:
            NSLog(@"Mail sent");break;
        case MFMailComposeResultFailed:
            NSLog(@"Mail sent failure: %@", [error localizedDescription]);
            break;
        default:
            break;
    }
    
    [controller dismissViewControllerAnimated:YES completion:NULL];
}

@end

Now I'll have to find out how to add the MessageuiFramework to my *.pro file to compile it usccessfully in QtCreator . But thats an other topic I guess.

[SGaist]

Hi,

On which line exactly do you have that failure ?
Which version of Qt are you using ?
Which version of Xcode ?
Which iOS version are you targeting ?

[J.Hilk]

Hi @SGaist ,
thanks for your time, I'm really a novice with objetcive-c so I'm struggeling quite a bit.

On which line exactly do you have that failure ?

that would be in this line:

- (void) showEmailPopup:(char *)aCStr{
    NSLog(@"LogMyMessage in Obj");
    NSLog([NSString stringWithUTF8String:aCStr]);

    //Email Subject
    NSString *emailTitle = @"Test Email";
    
    //Email Content
    NSString *messageBody = @"ios programming is so fun!";
    
    //To Address
    NSArray *toRecipents = [NSArray arrayWithObject:@"support@myCompany.com"];
    
    MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
    mc.mailComposeDelegate = self;
    
    [mc setSubject:emailTitle];
    [mc setMessageBody:messageBody isHTML:false];
    [mc setToRecipients:toRecipents];
    
//!---------------------This Line------------------
    [self presentViewController:mc animated:YES completion:NULL];
}

the xcode error is:

***Terminating app due to uncaught exception 'NSInvalidArgumentException', reason '-[MyObject presentViewController:animated:completion:] unrecognized selector sent to instance 0x1c001e8f0'

My guess would be I didn't initialize 'self' correctly ?

Which version of Qt are you using ?

I'm using Qt 5.10.1

Which version of Xcode ?

Version 9.2(9C40b)

Which iOS version are you targeting ?

Deployment Target is set to 10.0

[J.Hilk]

Ok, I made some changes in my code. It sill doesn't show the E-Mail Popup but it no longer crashes.

In the header file I changed

@interface MyObject : NSObject
{

}

//to
@interface MyObject : UIViewController <MFMailComposeViewControllerDelegate>
{

}

Aparently a NSOBject alone can not be the base of a ViewController?

however now I run int this error or warning as nothing happens:

Warning: Attempt to present <MFMailComposeViewController> on <MyObject> whose view is not in the window hierarchy!

So, how would I make it a defined part of the window hierarchy, when the rest of the UI is made by Qt-Code?

[J.Hilk]

Never mind, @SGaist , I managed to make it work.

//ObjectCInterface.h
#ifndef __OBJECTIVECINTERFACE_H__
#define __OBJECTIVECINTERFACE_H__

class MyClassImpl
{
public:
    MyClassImpl (void);
    ~MyClassImpl (void);

    void init (void);

    void showEmail(char * aCstr);

private:
    void * self;
};

#endif

//MyObject.h
#import "ObjectCInterface.h"
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <MessageUI/MessageUI.h>

@interface MyObject : UIViewController  <MFMailComposeViewControllerDelegate>
{

}

- (void)showEmailPopup:(char *) aCStr;

@end

//MyObject.mm
#import "MyObject.h"

@implementation MyObject


MyClassImpl::MyClassImpl( void ) : self(NULL){
    init();
}

MyClassImpl::~MyClassImpl( void ){
    [(id)self dealloc];
}

void MyClassImpl::init( void ){
    self = [ [MyObject alloc] init];
}


void MyClassImpl::showEmail(char *aCstr){
    NSLog(@"logMyMessage");
    [(id)self showEmailPopup:aCstr];
}


- (void) showEmailPopup:(char *)aCStr{
    NSLog(@"LogMyMessage in Obj");
    NSLog([NSString stringWithUTF8String:aCStr]);

    //Email Subject
    NSString *emailTitle = @"Test Email";
    
    //Email Content
    NSString *messageBody = @"ios programming is so fun!";
    
    //To Address
    NSArray *toRecipents = [NSArray arrayWithObject:@"support@MyCompany.com"];
    
    MFMailComposeViewController *mc = [[MFMailComposeViewController alloc] init];
    mc.mailComposeDelegate = self;
    
    [mc setSubject:emailTitle];
    [mc setMessageBody:messageBody isHTML:false];
    [mc setToRecipients:toRecipents];
    
    UIViewController * topController = [UIApplication sharedApplication].keyWindow.rootViewController;
    while (topController.presentedViewController){
        topController = topController.presentedViewController;
    }
    
    [topController presentViewController:mc animated:YES completion:NULL];
}


- (void) mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(nullable NSError *)error{
    switch (result) {
        case MFMailComposeResultCancelled:
            NSLog(@"Mail cancelled");
            break;
        case MFMailComposeResultSaved:
            NSLog(@"Mail saved");break;
        case MFMailComposeResultSent:
            NSLog(@"Mail sent");break;
        case MFMailComposeResultFailed:
            NSLog(@"Mail sent failure: %@", [error localizedDescription]);
            break;
        default:
            break;
    }
    
    [controller dismissViewControllerAnimated:YES completion:NULL];
}

@end

Now I'll have to find out how to add the MessageuiFramework to my *.pro file to compile it usccessfully in QtCreator . But thats an other topic I guess.

[SGaist]

ios {
    LIBS += -framework MessageUI
}