PromptForFile not working in OSX

Hallo
the plugin i am working on runs now on OSX (many thanks for the help on the cairo stuff!) but somehow this part dont work:


void doPopupFileDialog(){
IGraphics* gui = mPlug->GetGUI();
gui->PromptForFile(&samplefileName, kFileOpen, &sampleDir);
loadSoundfile();
};

simply nothing happens, on windows it works great...
this is on xcode 7.3 Mavericks
does anybody has a clue whats going on?
many thanks for some help!
styro

PromptForFile not working in OSX