如何在设备上写一个plist？目标C iphone

I have this code:

我有这个代码：

#define ALERT(X)    {UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Info" message:X delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];[alert show];[alert release];}

- (id)readPlist:(NSString *)fileName {  
    NSData *plistData;  
    NSString *error;  
    NSPropertyListFormat format;  
    id plist;  

    NSString *localizedPath = [[NSBundle mainBundle] pathForResource:fileName ofType:@"plist"];  
    plistData = [NSData dataWithContentsOfFile:localizedPath];   

    plist = [NSPropertyListSerialization propertyListFromData:plistData mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&error];  
    if (!plist) {  
        NSLog(@"Error reading plist from file '%s', error = '%s'", [localizedPath UTF8String], [error UTF8String]);  
        [error release];  
    }  

    return plist;  
}  

- (void)writeToPlist: (NSString*)a
{
    NSString *path = [[NSBundle mainBundle] bundlePath];
    NSString *finalPath = [path stringByAppendingPathComponent:@"data.plist"];
    NSMutableArray* pArray = [[NSMutableArray alloc] initWithContentsOfFile:finalPath];

    [pArray addObject:a];
    [pArray writeToFile:finalPath atomically: YES];
    ALERT(@"finished");
    /* This would change the firmware version in the plist to 1.1.1 by initing the NSDictionary with the plist, then changing the value of the string in the key "ProductVersion" to what you specified */
} 

- (void)viewDidLoad {
    [super viewDidLoad];
    [self writeToPlist:@"this is a test"];
    NSArray* the = (NSArray*)[self readPlist:@"data"];
    NSString* s = [NSString stringWithFormat:@"%@",the];
    ALERT(s);
    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}
#define ALERT(X)