[Interest] iOS Objective-C callback block example connecting back to iOS Qt app?

[Edward Sutton]

Hi Ben,

Thank you very much for sharing your example.

https://github.com/benlau/quickios/blob/master/qisystemutils.mm

Understanding the Objective-C language has been much more difficult than I expected coming from C, C++, and C#.

QMessageBox looks horrible on iOS.  I am very glad you have a solution for using UIAlertView in your alertViewCreate method.

UiActionSheet and UIImagePickerController

This has given me much to study and understand.

Thank you again for sharing your iOS code!

-Ed



On May 15, 2015, at 2:33 AM, Ben Lau <xbenlau at gmail.com<mailto:xbenlau at gmail.com>> wrote:

Hi Edward,

You may find example code from my project.

quickios/qisystemutils.mm at master · benlau/quickios<https://github.com/benlau/quickios/blob/master/qisystemutils.mm>

It has implemented an interface to create and communicate to UIAlertView , UIActionSheet , UIImagePickerController etc. It uses a singleton object called SystemMessenger as the bridge between C++ and Objective-C++ code. So that the developed code can be run on non-iOS platform too  (for development use)


On 15 May 2015 at 05:53, Edward Sutton <edward.sutton at subsite.com<mailto:edward.sutton at subsite.com>> wrote:
Can anyone share an example on how to implement the asynchronous return of a result from an Objective-C callback block to Qt?

For example, see the “successBlock:” below which gets called back asynchronously.

    self.PDFCreator = [NDHTMLtoPDF createPDFWithHTML:(NSString*)html
                                             baseURL:(NSURL*)baseUrl
                                          pathForPDF:[@"~/Documents/hello-world.pdf" stringByExpandingTildeInPath]
                                            pageSize:kPaperSizeA4 margins:UIEdgeInsetsMake(10, 5, 10, 5)
    successBlock:^(NDHTMLtoPDF *htmlToPDF) {

        NSString *result = [NSString stringWithFormat:@"HTMLtoPDF did succeed (%@ / %@)", htmlToPDF, htmlToPDF.PDFpath];
        NSLog(@"%@",result);
        self.resultLabel.text = result;

    }
    errorBlock:^(NDHTMLtoPDF *htmlToPDF) {
        NSString *result = [NSString stringWithFormat:@"HTMLtoPDF did fail (%@)", htmlToPDF];
        NSLog(@"%@",result);
        self.resultLabel.text = result;
    }];


Background:
————————

I need to implement native iOS code to replace the missing QPrinter functionality I used to convert HTML to a PDF report on Android, OS X, Linux, and Windows.

Unfortunately the Qt html-to-pdf functionality is implemented in QPrinter.  This functionality is gone from Qt iOS since iOS has no printer device support,  even though I am not accessing a printer device from iOS.

I found this project which seems to work:

        https://github.com/iclems/iOS-htmltopdf

Objective-C interfacing to C++ is challenging.

Thanks in advance for any tips,

-Ed
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