Rick's World

Ok, this truly sucks.

Last night, I was playing with Objective C. I had written an O-C class and tried to include a C++ class as a member variable of the O-C class. Now, you would think this would be possible, since you can create Objective-C++ classes that take advantage of certain C++ features. Apparently, this support of C++ in Objective-C is incomplete at best. I discovered that when I added that C++ class as a member variable, it compiled, but it gave me a warning telling me that the constructor and destructor of that member class would not be called! If the constructor and destructor don't get called, C++ classes are basically useless! What else won't get called on the C++ class in this case? This really sucks. This means that I had to basically rewrite that C++ class as a full Objective-C class in order to use it properly.

This, in my opinion is a glaring hole in the current implementation of Objective-C. It seems inconceivable to me that you can easily include any C code you want, but only certain parts of C++ work in Objective-C. I really hope they fix this in Objective-C 2.0, that is coming Real Soon Now, in Leopard!

Yeah, yeah, I know. I spend most of my time using OS X these days, but on occasion I do some 'slumming' in the Windows world. I do program Windows for a living, after all. Yesterday, I downloaded Microsoft's new Virtual PC 2007. I wanted to try it because it supports hardware virtualization. This means that the virtual PC that you run should run nearly as fast as your main PC. I wanted to give my first impressions of it.

So far, my first impression is not good. I downloaded Ubuntu Linux as an ISO image. Once installed, I launched Virtual PC 2007 with the ISO image mounted as the CD ROM drive. The virtual machine booted up and Ubuntu seemed to install properly. Once Ubuntu rebooted however, things got bizarre. The virtual machine window expanded to a little wider than my screen size of 1600x1200 and less than half of my screen height. (1600x400? what kinda resolution is that???) I tried everything to get it to work with no luck.

Once Ubuntu failed, I decided to try another Linux, so I downloaded Open Suse. I created a new virtual machine for it, mounted the ISO image again and 'rebooted' the virtual machine. Open Suse came up, got to the splash screen and just stopped. I rebooted several times and trie again with no luck. Finally I rebooted and forced Open Suse to 800x600 resolution. That seemed to do the trick. I left it installing when I left for work this morning. We'll see how it goes.

Another odd and really annoying thing about Virtual PC 2007 is that if you choose 'other' as the type of operating system to install, it defaults to only giving the machine 128MB! That is way too little amount of RAM! Can you imagine trying to run any relatively modern operating system with that little amount of RAM? It'll never happen.

My current theory is that VPC is having some kind of problem with virtual screen resolutions... If you let it 'autodetect' the resolution, it doesn't seem to work right, but if you force it to a certain resolution, it seems to work better.

Why did I call this article 'Bleeding Edge Virtualization'? Because not only am I using a brand new virtual machine app, I'm also trying to run it on Microsoft Vista - a brand new operating system. Maybe the two don't 'get along' very well. I didn't check this, but since Virtual PC 2007 was supposed to be a part of Vista Ultimate Edition, naturally I assumed they would work together. I'll have to try installing a version of Windows in a virtual machine and see what happens... Somehow I think that will go much better. :(

For all the Microsoft developers out there, you can download a free copy of the MSDN Library here.

A delegate is a kind of 'helper class' in Cocoa. Very often in Cocoa, you won't subclass a class, instead you'll just use the base class and register yourself as a delegate. This means that whenever interesting events happen in the base class, it calls a method on the delegate. The return value of this delegate function allows you to notify the calling class to stop or continue various operations.

Of course, you can create your own classes in Cocoa. This means that there needs to be a way to add support for delegate processing in your custom class. Here are the steps necessary to make this work.

1. Declare the delegate variable and accessor methods in your class' header file. Note that these accessor methods should follow the standard Cocoa Key Value Coding scheme.

   @interface ClassName : NSObject 
   {
       id delegate;
   }
   
   - (void)setDelegate:(id)val;
   - (id)delegate;
   
   @end
   

2. Define the accessor functions in your implementation file.

   @implementation ClassName
   
   - (void)setDelegate:(id)val
   {
       delegate = val;
   }
   
   - (id)delegate
   {
       return delegate;
   }
   
   @end
   

3. Create an informal protocol that contains all the delegate functions that your class will call in the delegate object. This informal protocol is implemented as a Category on the NSObject class. Note that the delegate will work without this step, but if you leave this out, XCode will generate a lot of "warning: no '-XXX' method found" warning messages. Also, your class that acts as the delegate of this class does not have to implement all these delegate functions. It only has to implement the methods that it is interested in. The rest will simply be ignored.

   @interface NSObject (ClassName)
   
   - (void)delegateFunction1;
   - (void)delegateFunction2;
   // etc...
   
   @end
   

4. Before calling a delegate method, make sure the delegate supports that method by using the respondsToSelector: message.

   - (void)someMethod 
   {
       if ( [delegate respondsToSelector:@selector(delegateFunction1:)] ) 
       {
           [delegate delegateFunction1];
       }
   }
   

Here's how to do exceptions in Cocoa... It's nearly identical to C++ exceptions:

@try
{
    // Do some code here that might throw an exception.
}
@catch( NSException* e )
{
    // Log the exception. 
    NSLog( @"Exception: %@, %@", [e name], [e reason] );
}

One important thing to remember when doing these types of exceptions is that it will only work for apps written for OS X 10.3 (Panther) or later. This shouldn't be a problem, though.

Also, in order to get these to work, you need to turn on Objective-C exceptions in the XCode Build settings. The easiest way to do this is to bring up the Project Info dialog box, click on the 'Build' tab, then use the search box in the upper right to search for 'exception'. The last one should say 'Enable Objective-C Exceptions'. Click that item to put a check box in the box, rebuild and you are done.

In the XCode editor, if you hold down the Option key (which is the Alt key on PC keyboards) and double click a class name or method, it will look up that word in the API documentation. This is great way to look up the info on a class method.

Here's how to do a mutex when writing a multithreaded Cocoa app. Use the NSLock class...

// In your class' header. (ClassName.h)
@interface ClassName: NSObject
{
    NSLock*     mutex;
}

// In your class' source. (ClassName.m)
@implementation ClassName

- (id)init
{
    if ( (self = [super init] ) ) 
    {
        mutex = [[NSLock alloc] init];
        
        // Other initialization stuff here..
    }
    return self;
}

- (void)dealloc
{
    if ( mutex )
    {
        [mutex release];
        mutex = NULL;
    }

    // Other cleanup code here...
	
    [super dealloc];
}


- (void)someFunction
{
    [mutex lock];

    // Do some stuff.

    [mutex unlock];
}

Ok, so I've been learning Mac programming using Objective-C. I'm still a horrible rank amateur at this stuff, but here's one thing I've learned. Here is an example of how to display a modal File Open dialog box...

int i; // Loop counter.

// Create the File Open Dialog class.
NSOpenPanel* openDlg = [NSOpenPanel openPanel];

// Enable the selection of files in the dialog.
[openDlg setCanChooseFiles:YES];

// Enable the selection of directories in the dialog.
[openDlg setCanChooseDirectories:YES];

// Display the dialog.  If the OK button was pressed,
// process the files.
if ( [openDlg runModalForDirectory:nil file:nil] == NSOKButton )
{
    // Get an array containing the full filenames of all
    // files and directories selected.
    NSArray* files = [openDlg filenames];

    // Loop through all the files and process them.
    for( i = 0; i < [files count]; i++ )
    {
        NSString* fileName = [files objectAtIndex:i];

        // Do something with the filename.
    }
}

I wrote previously about how other sites were linking directly to the images on my site from their pages without my permission. Yeah, I suppose I could just delete the images, but I figured I'd get a little free advertising out of it. I just updated all my images on the site to include a small watermark that contains my web site URL.

I mentioned briefly in my previous blog that I need to do something to mark my images with my website URL, so that when people link directly to my images, it shows my web site on the image. Credit were credit is due. The way you do this is by putting a watermark on the image. A watermark is a text overlay on the image. I found an app called ImageWell for OS X that looks like it will do the trick.

I'm going to fix those images tonight.