How to retain a plist file in memory

Question

I'm loading a plist file using a slightly tweaked version of the example in the developer docs

- (void) loadPlistIntoMemory
{

    NSString *errorDesc = nil;
    NSPropertyListFormat format;
    NSString *plistPath;

    NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    plistPath = [rootPath stringByAppendingPathComponent:@"bullionrun.plist"];

    // check to see if the plist exists in the documents directory, if not, get it from the bundle
    if (![[NSFileManager defaultManager] fileExistsAtPath:plistPath]) {
        NSLog(@"Property List not found. Looking for property list in Bundle.");
        NSString * plistBundlePath = [[NSBundle mainBundle] pathForResource:@"bullionrun" ofType:@"plist"];

        // Copy it to the document folder and read it from there
        [[NSFileManager defaultManager] copyItemAtPath:plistBundlePath toPath:plistPath error:nil];

    }else {
        NSLog(@"Property List found in Documents Folder");
    }


    // Read the data in the plist
    NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];

    NSDictionary *temp = (NSDictionary *)[NSPropertyListSerialization
                                           propertyListFromData:plistXML 
                                           mutabilityOption:NSPropertyListMutableContainersAndLeaves 
                                           format:&format 
                                           errorDescription:&errorDesc];

    // If Error
    if (!temp) {
        NSLog(@"Error reading plist: %@, format: %d", errorDesc, format);
    }else {
        NSLog(@"Property List OK");
        // store the plist data
        [self setPlistData:temp];

    }


}

Now, that works fine, but when I need to access PlistData later on, it's been deallocated. The header file looks like this

@interface Registry : NSObject {

    NSDictionary        *   _plistData;


}

@property (nonatomic, retain) NSDictionary * plistData;

and the @synthesize bit looks like this @synthesize plistData = _plistData;.

I struggle with memory management all the time. I just can't get my head around it (I'm not a natural programmer at all, I just like it), But I thought that by using retain in the header file when I declare the plistData property, that it would be retained.

Clearly not though, since any attempt to access it later (eg NSLog(@"%@", self.plistData)) results in an error...

-[CFString hash]: message sent to deallocated instance 0x6436560

I've also tried creating a manual setPlistData method that chucks a retain in there, but that crashes the app without an error.

Can anyone give me a nudge in the right direction?