ios - 'sizeWithFont:constrainedToSize:lineBreakMode:'is deprecated:

Question

Converting a project from iOS5.0 to iOS7 / iOS6 on Xcode 5. The code below is giving a compile time warning:

'sizeWithFont:constrainedToSize:lineBreakMode:'is deprecated: first deprecated in ios 7.0 - Use - boundingRectWithSize:options:attribiutes:context

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.section == 0)
    {
        self.lblHidden.frame = CGRectMake(58, 228, 945, 9999);
        self.lblHidden.text = detailShareObj.pDesc;
        CGSize size = [detailShareObj.pDesc sizeWithFont:self.lblHidden.font constrainedToSize:self.lblHidden.frame.size lineBreakMode:NSLineBreakByWordWrapping];
        return 228.0+size.height+20;

    }
    else if (indexPath.section == 1)
    {
        NSString *tempPointStr = (self.shortDescArray)[indexPath.row];

        self.lblHidden.frame = CGRectMake(58, 0, 945, 9999);
        self.lblHidden.text = tempPointStr;
        CGSize size = [tempPointStr sizeWithFont:self.lblHidden.font
                               constrainedToSize:self.lblHidden.frame.size
                                   lineBreakMode:NSLineBreakByWordWrapping];

            return 50.0f;
    }

I tried some of the suggestion give elsewhere but nothing is up to rescue if some one can help by giving the corrections required in the code will be greatly appreciated.

Answer 1

I wouldn't just mask the deprecated function warning. They deprecated it for a reason. I believe the function was deprecated because that series of NSString+UIKit functions were based on the UIStringDrawing library, which wasn't thread safe. If you tried to run them not on the main thread (like any other UIKit functionality), you'll get unpredictable behaviors. In particular, if you ran the function on multiple threads simultaneously, it'll probably crash your app. This is why in iOS 6, they introduced a the boundingRectWithSize:... method for NSAttributedStrings. This was built on top of the NSStringDrawing libraries and is thread safe.

If you look at the new NSString boundingRectWithSize:... function, it asks for an attributes array in the same manner as a NSAttributeString. If I had to guess, this new NSString function in iOS 7 is merely a wrapper for the NSAttributeString function from iOS 6.

On that note, if you were only supporting iOS 6 and iOS 7, then I would definitely change all of your NSString's sizeWithFont:... to the NSAttributeString's boundingRectWithSize. It'll save you a lot of headache if you happen to have a weird multi-threading corner case! Here's how I converted NSString's sizeWithFont:constrainedToSize::

What used to be:

NSString *text = ...;
CGFloat width = ...;
UIFont *font = ...;
CGSize size = [text sizeWithFont:font 
               constrainedToSize:(CGSize){width, CGFLOAT_MAX}];

Can be replaced with:

NSString *text = ...;
CGFloat width = ...;
UIFont *font = ...;
NSAttributedString *attributedText =
    [[NSAttributedString alloc]
        initWithString:text
        attributes:@
        {
            NSFontAttributeName: font
        }];
CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];
CGSize size = rect.size;

Please note the documentation mentions:

In iOS 7 and later, this method returns fractional sizes (in the size component of the returned CGRect); to use a returned size to size views, you must use raise its value to the nearest higher integer using the ceil function.

So to pull out the calculated height or width to be used for sizing views, I would use:

CGFloat height = ceilf(size.height);
CGFloat width  = ceilf(size.width);