objective c - With what should I replace the deprecated sizeWithFont: method?

Question

I have a method that gives me the perfect size for a UITextView given a length of string (with the corresponding correct font size) :

- (NSInteger) heightOfLabel:(NSString*) string {
    CGSize maximumLabelSize = CGSizeMake([[UIScreen mainScreen] bounds].size.width - 40, FLT_MAX);
    CGSize expectedLabelSize = [[NSString stringTrimmedForLeadingAndTrailingWhiteSpacesFromString:string]
             sizeWithFont:[UIFont systemFontOfSize:15]
             constrainedToSize:maximumLabelSize 
             lineBreakMode:NSLineBreakByWordWrapping];

    return expectedLabelSize.height + 5;
}

In fact, it still gives me a perfect fit, even in iOS7. Although now it comes up with a warning method that says I shouldn't use 'sizeWithFont:contrainedToSize:lineBreakMode'.

It now says I should be using -boundingRectWithSize:options:attributes:context:

This method isn't new to iOS7 and therefore i figure that it is okay to ask it on stack overflow, rather than going across to the official apple developers forum.

I have three questions:

1) Because it is deprecated, does that mean I should definitely replace it, despite it still working?

2) I have tried many different boundingRectWithSize: methods, with various variables but it is never perfect, it always seems to be slightly out (as many stackoverflow questions point out) - is there a perfect replacement with this none-deprecated method that does exactly the same as my previous method with as minimal hassle?

3) why remove this method? Is it because of the overlap with this other method?

Answer 1

After an hour of trial error I managed to make it work:

CGSize maximumLabelSize = CGSizeMake(tableView.width, MAXFLOAT);

NSStringDrawingOptions options = NSStringDrawingTruncatesLastVisibleLine |
                                 NSStringDrawingUsesLineFragmentOrigin;

NSDictionary *attr = @{NSFontAttributeName: [UIFont systemFontOfSize:15]};
CGRect labelBounds = [string boundingRectWithSize:maximumLabelSize 
                                          options:options
                                       attributes:attr
                                          context:nil];

Update:

As Mr. T mentions in answer below : 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. ceilf function is recommended to use.

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