Why can't I release my CTFramesetter without the app crashing?

Question

I'm building an iPad app which renders pages of text from an NSAttributedString. I create a framesetter like this:

- (void)renderTextFromAttributedString:(NSAttributedString *)string
{
    CFAttributedStringRef attrString = (CFAttributedStringRef)string;
    framesetter = CTFramesetterCreateWithAttributedString(attrString);
    CFRelease(attrString);

... then the code adds new page views, one by one, and passes the framesetter pointer off to each one to render each page, until there are no characters left:

- (void)drawNewPage
{
    CTSinglePageView *newPage = [[CTSinglePageView alloc] initWithFrame:newFrame];
    newPage.delegate = self;
    [newPage renderWithFramesetter:framesetter fromIndex:currentIndex margins:self.margins];
    [self addSubview:newPage];
    [newPage release];
    currentPage ++;

... etc etc. Now this all works great, rendering the pages and showing the formatted text perfectly. However, at the end of the render process, I've still got a CTFramesetter which needs clearing, so I can build the next set of pages. However, if I do

    if(framesetter) CFRelease(framesetter);

at the end of the process, the CTFramesetter is released (obviously) and the program crashes! BUT... If I don't release the framesetter, I eventually get rather large memory leaks and the program bails out.

Why is the release causing a crash? With NSZombieEnabled turned on, the error message I get is:

* -[NSConcreteAttributedString release]: message sent to deallocated instance 0xed20270

Any help given is of course greatly received! We are currently up against a deadline here, if I could add a bounty now I would! Anyone with a good answer will be rewarded a bounty after the 2 day window has elapsed. :-)

Answer 1

Are you sure you're supposed to be releasing attrString? That doesn't look right. I wonder if that's causing the crash later when releasing framesetter.