-writeToURL is not overwriting the previous write

Question 1

I figured it out... for others that are having the same problem, here is the code that works. Notice that I do NOT save it to a temporary file, since I already have the image in the Core Data entity. Here's the code:

-(void) showExistingAppointmentDetails: (AppointmentInfo *) apptSelected  {

//  make rectangle to attach popover
CGRect rectangle = CGRectMake( [apptSelected.aPosX floatValue], [apptSelected.aPosY floatValue],
                              [apptSelected.aPosW floatValue], [apptSelected.aPosH floatValue]);

//  see if this is for staff; if so, don't display anything
if([apptSelected.aApptKey isEqual: @"Staff"])
    return;

NSPredicate *predicate =  ([NSPredicate predicateWithFormat: @"aClientKey == %@", apptSelected.aApptKey ]);  //  was aApptKey
ClientInfo *client = [ClientInfo MR_findFirstWithPredicate:predicate inContext:localContext];

UIImage *image = [UIImage imageWithData:client.aClientImage];  //  image is good  <---------

//  write appointment info into html string
NSString *htmlString;
if(client.aClientEMail.length > 0)  {
    htmlString = [NSString stringWithFormat:NSLocalizedString(@"HTML_STRING1",nil),
                  client.aClientFirstName,
                  client.aClientLastName,
                  client.aClientEMail.length == 0? @"": client.aClientEMail,
                  client.aClientPrimaryPhone,
                  apptSelected.aServices,
                  [self htmlForPNGImage:image]];
}
else  {
    htmlString = [NSString stringWithFormat:NSLocalizedString(@"HTML_STRING2",nil),
                  client.aClientFirstName,
                  client.aClientLastName,
                  client.aClientPrimaryPhone,
                  apptSelected.aServices,
                  [self htmlForPNGImage:image]];

}

UIViewController* popoverContent = [[UIViewController alloc] init];
UIView* popoverView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 250, 300)];
popoverView.backgroundColor = [UIColor colorWithWhite:(CGFloat)1.0 alpha:(CGFloat)1.0];  //  frame color?
popoverContent.view = popoverView;

//resize the popover view shown in the current view to the view's size
popoverContent.contentSizeForViewInPopover = CGSizeMake(250, 300);

//  add the UIWebView for RichText
UIWebView *webView = [[UIWebView alloc] initWithFrame:popoverView.frame];
webView.backgroundColor = [UIColor whiteColor];  //  change background color here

//  add the webView to the popover
[webView loadHTMLString:htmlString baseURL:[NSURL URLWithString:nil]];
[popoverView addSubview:webView];

//  if previous popoverController is still visible... dismiss it
if ([popoverController isPopoverVisible]) {
    [popoverController dismissPopoverAnimated:YES];
}

//create a popover controller
popoverController = [[UIPopoverController alloc] initWithContentViewController:popoverContent];
[popoverController presentPopoverFromRect:rectangle inView:self
                 permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];

}


- (NSString *) htmlForPNGImage:(UIImage *) image {

NSData *imageData = UIImagePNGRepresentation(image);
NSString *imageSource = [NSString stringWithFormat:@"data:image/png;base64,%@",[imageData base64Encoding]];
return [NSString stringWithFormat:@"%@", imageSource];

}

Question 2

you never write the data to disk as far as I can see.

Only in the commented out section you attempt to.

Write it in between:

NSURL *tmpDirURL = [NSURL fileURLWithPath:NSTemporaryDirectory() isDirectory:YES];
NSURL *fileURL = [[tmpDirURL URLByAppendingPathComponent:@"custImage"] URLByAppendingPathExtension:@"png"];    
//write 
NSError*writeError = nil;
[client.aClientImage writeToURL:fileURL options:0 error:&writeError];
NSAssert(writeError==nil, writeError);

//read / use in the html or so 
...

Dont forget to reload the web view or whatever you use to show the html