NSString boundingRectWithSize slightly underestimating the correct height - why?

Question

I\'m attempting to resize a text field / view automatically depending on its current width. In other words I want the width to stay constant but resize the height according

Answer 1

I had the same Problem. I found the following in the Documentation:

To correctly draw and size multi-line text, pass NSStringDrawingUsesLineFragmentOrigin in the options parameter.

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

So this solved it for me:

CGRect rect = [myLabel.text boundingRectWithSize:CGSizeMake(myLabel.frame.size.width, CGFLOAT_MAX)
                                                            options:NSStringDrawingUsesLineFragmentOrigin
                                                            attributes:@{NSFontAttributeName: myLabel.font}
                                                            context:nil];
rect.size.width = ceil(rect.size.width);
rect.size.height = ceil(rect.size.height);

Update (Swift 5.1)

An alternative Swift way to do this would be:

let size = myLabel.text!.size(
    withAttributes: [.font: myLabel.font!]
)
let rect = CGSize(
  width: ceil(size.width),
  height: ceil(size.height)
)

See this answer for an Objective-C example.