Question

I’m reading this article about creating a global hotkey. I’ve gone through the tutorial successfully, but now I’m trying to message an Objective-C method, and I’m stuck. Is there a way to message Objective-C from C++ code?

http://cocoasamurai.blogspot.com/2009/03/global-keyboard-shortcuts-with-carbon.html

Here’s where my code is at:

#import "AppDelegate.h"
#import <Carbon/Carbon.h>

@implementation AppDelegate

@synthesize window = _window;
@synthesize statusItem;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    EventHotKeyRef myHotKeyRef;
    EventHotKeyID myHotKeyID;
    EventTypeSpec keyPressedEventType;
    EventTypeSpec keyReleaseEventType;

    keyPressedEventType.eventClass=kEventClassKeyboard;
    keyPressedEventType.eventKind=kEventHotKeyPressed;

    keyReleaseEventType.eventClass=kEventClassKeyboard;
    keyReleaseEventType.eventKind=kEventHotKeyReleased;

    InstallApplicationEventHandler(&keyPressedHandler, 1, &keyPressedEventType, NULL, NULL);
    InstallApplicationEventHandler(&keyReleasedHandler, 1, &keyReleaseEventType, NULL, NULL);

    myHotKeyID.signature='mhk1';
    myHotKeyID.id=1;

    RegisterEventHotKey(97, 0, myHotKeyID, GetApplicationEventTarget(), 0, &myHotKeyRef);
}

- (void)awakeFromNib
{
    statusItem = [[NSStatusBar systemStatusBar] statusItemWithLength:NSVariableStatusItemLength];
    [statusItem setMenu:statusMenu];
    [statusItem setImage:[NSImage imageNamed:@"microphone_muted"]];
    [statusItem setAlternateImage:[NSImage imageNamed:@"neg_microphone_muted"]];
    [statusItem setHighlightMode:YES];
}
- (void) mute
{
    [statusItem setImage:[NSImage imageNamed:@"microphone_muted"]];
    [statusItem setAlternateImage:[NSImage imageNamed:@"neg_microphone_muted"]];
}
- (void) unmute 
{
    [statusItem setImage:[NSImage imageNamed:@"microphone"]];
    [statusItem setAlternateImage:[NSImage imageNamed:@"neg_microphone"]];
}
OSStatus keyPressedHandler(EventHandlerCallRef nextHandler, EventRef anEvent, void *userData)
{   
    NSLog(@"Unmute mic");
    return noErr; 
}
OSStatus keyReleasedHandler(EventHandlerCallRef nextHandler, EventRef anEvent, void *userData)
{
    NSLog(@"Mute mic");
    return noErr; 
}
@end

Answer 1

If your C++ source files have the extension .mm (instead of .cpp), then it will be compiled as Objective-C++, and you will be able send messages to your Objective-C objects just as if you were using a standard .m source file.