Python for Bioinformatics: Instant Cocoa: Checkbook project 3

Wednesday, October 14, 2009

Instant Cocoa: Checkbook project 3

Saving NSData

If you make a document-based Cocoa project, you need to implement methods in MyDocument (or whatever you want to call it) to do the save and reloading. We talked the other day about what is needed to get an icon on the saved file and make it able to launch the app when double-clicked. In that post we used

writeToURL: ofType: error:
readFromURL: ofType: error:

This is a different approach to saving, using NSData. Here are the two functions to be implemented (note that they do not need to be re-declared). The model data is contained in a @synthesized variable called checkbookItemsArray. The try / catch code is straight out of Hillegass:

- (NSData *)dataOfType:(NSString *)typeName 
            error:(NSError **)outError{
    return [NSKeyedArchiver
        archivedDataWithRootObject:checkbookItemsArray];
}

- (BOOL)readFromData:(NSData *)data
              ofType:(NSString *)typeName
               error:(NSError **)outError {
    NSLog(@"about to read data of type %@", typeName);
    @try {
        dataIn = [NSKeyedUnarchiver 
                     unarchiveObjectWithData:data];
    }
    @catch (NSException * e) {
        if (outError) {
            NSDictionary *d = [NSDictionary 
                dictionaryWithObject:@"The data is corrupted"
                    forKey:NSLocalizedFailureReasonErrorKey];
            *outError = [NSError 
                errorWithDomain:NSOSStatusErrorDomain
                           code:unimpErr
                       userInfo:d];
        }
        return NO;
    }
    [self setCheckbookItemsArray:dataIn];
    [myBalancer calculateBalance:checkbookItemsArray];
    [myTV deselectAll:self];
    return YES;
}