Unable to setObject:forKey: in NSMutableDictionary - iphone

Question

I'm sure I'm missing something obvious here in a simple iPhone program I'm trying to write, but the code seems so basic that I can't see what's wrong.
I'm trying to use an NSMutableDictionary to store a list of classes and their associated save file names. In the header file I declare the dictionary
#interface ClassList : UITableViewController {
NSString *homedirectory;
NSString *masterindexpath;
NSMutableDictionary *classFilenameGlossary;
NSMutableArray *listofclasses;
}
#property (retain, nonatomic) NSString *homedirectory;
#property (retain, nonatomic) NSString *masterindexpath;
#property (retain, nonatomic) NSMutableDictionary *classFilenameGlossary;
#property (retain, nonatomic) NSMutableArray *listofclasses;
And, of course, in the implementation file:
#implementation ClassList
#synthesize homedirectory;
#synthesize masterindexpath;
#synthesize classFilenameGlossary;
#synthesize listofclasses;
I initialize this dictionary at ViewDidLoad from an existing file that saves the classlist:
- (void)viewDidLoad {
[super viewDidLoad];
// Get home directory
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
homedirectory = [paths objectAtIndex:0];
masterindexpath = [homedirectory stringByAppendingPathComponent:#"MasterIndex"];
// Get master course list or create it if necessary
NSFileManager *fm = [NSFileManager defaultManager];
if ([fm fileExistsAtPath:masterindexpath] == NO)
{
NSMutableDictionary *temporarydictionary = [NSMutableDictionary dictionary];
[temporarydictionary writeToFile:masterindexpath atomically:NO];
[temporarydictionary release];
}
[classFilenameGlossary initWithContentsOfFile:masterindexpath];
[homedirectory retain];
[masterindexpath retain];
}
Later, I add an item using setObject:forKey: but the dictionary never changes. Originally I was doing this in another view controller using a pointer back to this ClassList file, but once I discovered that didn't work, I simplified and tried to just set any sample object and key within the ClassList file:
[classFilenameGlossary setObject:#"sample filename" forKey:#"sample classname"];
I've looked at the debugger variable list and it shows classFilenameGlossary properly identified as an NSMutableDictionary with 0 key/value pairs. I'm not getting any sort of error; the dictionary simply never changes. At the moment, the dictionary loaded from the file masterindexpath is empty (since I haven't been able to add any items yet), but that shouldn't keep me from being able to add items to the dictionary.
I'm a total beginner at iPhone programming, so I'm sure there's something basic that I'm missing. I'd appreciate any help.

Answer 1

This line:
[classFilenameGlossary initWithContentsOfFile:masterindexpath];
should look like this:
classFilenameGlossary = [[NSMutableDictionary alloc] initWithContentsOfFile:masterindexpath];
You forgot to allocate memory for the NSMutableDictionary, so that's why it never initializes.