Question

I am getting the following error:

I can’t seem what is wrong with my code. Here’s some code in my AHInstagramImageData

-(id)initWithData:(NSDictionary *)data
{
    self = [super init];
    if (!self) {
        return nil;
    }

for (NSDictionary * comment in imgCmt){
        AHInstagramImageComment * instagramImgComment  = [[AHInstagramImageComment alloc] initWithData:comment];
        [comments insertObject:instagramImgComment atIndex:0];
        [instagramImgComment release];
    }
}

and then on the AHInstagramImageComment I have:

-(id)initWithData:(NSDictionary *)data
{
    self = [super init];
    if (!self) {
        return nil;
    }

    [self calculateCommentsHeight];

    return self;
}

- (void) calculateCommentsHeight
{
    NSString *combinedComment = [NSString stringWithFormat:@"%@ %@", self.username, self.text];
    CGFloat desiredHeight = [combinedComment sizeWithFont:[UIFont fontWithName:@"HelveticaNeue" size:14] constrainedToSize:CGSizeMake(kCommentsMaxWidth, CGFLOAT_MAX) lineBreakMode:UILineBreakModeClip].height;

    if (desiredHeight >= 50){
        commentHeight_ = desiredHeight;
    } else {
        commentHeight_ = 50;
    }

    commentHeight_ += kTimestampMaxHeight;
    commentHeight_ += 5;
}

So essentialy I had initializing the AHInstagramImageData in a background queue:

 [weakSelf.backgroundQueue_ addOperationWithBlock:^{
                             NSArray *arr = [response valueForKey:@"data"];
                             int startingIndex = [[AHImageDataSource sharedDataSource] count];
                             for (NSDictionary * data in arr){
                                 AHInstagramImageData * imgData = [[AHInstagramImageData alloc] initWithData:data];

}
}];

Is any of these wrong ?

Answer 1

I had a problem similiar to this before. There is currently a bug which prevents [NSString sizeWithFont:] and [NSString drawInRect:] to run on background threads, or via NSOperations.

See this link:
Bug in UIKit string drawing method?

You have a few options:

1. Don’t use sizeWithFont: with NSOperations.

2. Set max operation count on your NSOperationQueue to 1:

   [queue setMaxConcurrentOperations:1];

3. Use Core Text and NSAttributedStrings, which have their own “sizeWithFont” method: CTFramesetterSuggestFrameSizeWithConstraints

4. Use [NSOperationQueue mainQueue]; to run operations on the main thread.