Using delegate

[azaturkmen]

Hi,

I am new in Qt C++. I want to use a delegate feature as in Objective-C. How can I use such a thing?

[brandont]

See "Wikipedia":http://en.wikipedia.org/wiki/Delegation_pattern#Complex_C.2B.2B_example . Is that what you mean?

[DenisKormalev]

Don't know how ObjC implements delegation, but if we are speaking about OO delegation mechanism, then maybe you can do what you need with signal-slots mechanism?

[azaturkmen]

I have IconDownloader class. it downloads image asyncranously and i want it to trigger owner class's method.

@Objective-C

• (void)showImage:
  {
  IconDownloader *iconDownloader = [[IconDownloader alloc] init];
  iconDownloader.imageUrl = "http://www.a.com./image.jpg";
  iconDownloader.delegate = self;
  [iconDownloader startDownload];
  [iconDownloader release];
  }

// called by our IconDownloader class when an icon is ready to be displayed

• (void)appImageDidLoad:(NSIndexPath *)indexPath
  {
  ....
  }
  @

[Franzk]

Use "signals & slots":http://doc.trolltech.com/latest/signalsandslots.html as Denis proposed.

[azaturkmen]

thanks for help :)

I understand now. we can declare our own signals. ok.