memory management for CTRunDelegateRef iPhone

Question

I focus on a project to add image support based on OmniGroup's rtf editor.I met the problem when I use CTFramesetterCreateWithAttributedString , and it receives

EXC_BAD_ACCESS

which is caused by a zombie object.

For simplicity, I get the NSAttributedString from a rtfd file which only has a photo. I add the method to parser the image tag on iOS based on the Omni's sample. And the part to create the NSAttributedString is followed by this tutorial from raywenderlich , and looks like:

    CTRunDelegateCallbacks callbacks;
    callbacks.version = kCTRunDelegateCurrentVersion;
    callbacks.getAscent = ascentCallback;
    callbacks.getDescent = descentCallback;
    callbacks.getWidth = widthCallback;
    callbacks.dealloc = deallocCallback;
    CTRunDelegateRef delegate = CTRunDelegateCreate(&callbacks, imgAttr); 

    NSDictionary *imgAttr = [NSDictionary dictionaryWithObjectsAndKeys:imgWidth,kImageWidth,imgHeight,kImageHeight, nil];//recored the width and height
    NSDictionary *attrDictionaryDelegate = [NSDictionary dictionaryWithObjectsAndKeys:(id)delegate, (NSString*)kCTRunDelegateAttributeName,nil];
     [_attributedString appendString:@" " attributes:attrDictionaryDelegate];
     CFRelease(delegate);

here appendString:attributes: is provided by Omni and is a category for NSMutableAttributedString :

- (void)appendString:(NSString *)string attributes:(NSDictionary *)attributes;
{
    NSAttributedString *append;

    append = [[NSAttributedString alloc] initWithString:string attributes:attributes];
    [self appendAttributedString:append];
    [append release];
}

In the Parser class I test CTFramesetterCreateWithAttributedString and it creates successfully and no memory problem happens. However, when I call CTFramesetterCreateWithAttributedString in my view class, it receives the EXC_BAD_ACESS problem. I send the CTFramesetterCreateWithAttributedString to my view in the viewDidLoad:

NSArray *arr = [OUIRTFReader parseRTFString2:rtfString];
self.editFrame.attributedText = [arr objectAtIndex:0];


//for OUIRTFReader
+ (NSArray *)parseRTFString2:(NSString *)rtfString
{
    OUIRTFReader *parser = [[self alloc] _initWithRTFString:rtfString];
    NSMutableArray *temp  = [NSMutableArray arrayWithCapacity:1];
    NSAttributedString *tempAstr = [[NSAttributedString alloc] initWithAttributedString:parser.attributedString];

    [temp addObject:tempAstr];
    [tempAstr release];
    if (parser.zjImageArray) {
        [temp addObject:parser.zjImageArray];
    }

    [parser release];
}

here editFrame is ivar of OUIEditableFrame provided by OmniFramework. After that, in the layoutSubview: of OUIEditableFrame , CTFramesetterCreateWithAttributedString failed. Profiling with instrument, it points there is a zombie object in :

NSDictionary *imgAttr = [NSDictionary dictionaryWithObjectsAndKeys:imgWidth,kImageWidth,imgHeight,kImageHeight, nil];

It demonstrates that

An Objective-C message was sent to a deallocated object(zombie) at address

I'm not so familiar with core foundation like as UIKit or others. So I'd like to know what's wrong with the method to create a attributed string for image with CTRunDelegateRef in my code?

Thanks!

Answer 1

CTRunDelegateCreate create a delegate with an arbitrary context pointer ( void * ). That means the dictionary imgAttr isn't retained by the delegate.

You need to retain the context dictionary when creating the delegate and release it in the dealloc callback.