Calculating attributed string height - ios

Question

I'm trying to set a tableViewCell height equal to the height of the attributedString inside the cell. However whatever I do it does not seem to have the correctSize. this is what I've tried so far
cellHeight
//Convert description to NSAttributedString and get height
//width is equal to screen width - right and left offset
//at the end add the bottom and height offset to the cell height
return detailPetViewModel!.description
.lineSpacing(spacing: 4)
.heightWithConstrainedWidth(width: Sizes.screenWidth - 40) + 10
Customize descLabel in cell subclass
//Customize descLabel
descLabel.font = FontFamily.Avenir.Regular.font(size: 16)
descLabel.textColor = UIColor(named: .SecondaryTextColor)
//Multiple lines
descLabel.numberOfLines = 0
descLabel.lineBreakMode = .byWordWrapping
descLabel.sizeToFit()
linespacing extension
extension String {
func lineSpacing(spacing: CGFloat) -> NSAttributedString {
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = spacing
let attributedString = NSMutableAttributedString(string: self)
attributedString.addAttribute(NSParagraphStyleAttributeName, value:paragraphStyle, range:NSMakeRange(0, attributedString.length))
return attributedString
}
}
height Extension
extension NSAttributedString {
func heightWithConstrainedWidth(width: CGFloat) -> CGFloat {
let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, context: nil)
return boundingBox.height
}
}

Answer 1

This is the extension I use. You shouldn't have to pass in any information about the font or line-height as the attributed string already knowns its values.
extension NSAttributedString {
func height(containerWidth: CGFloat) -> CGFloat {
let rect = self.boundingRect(with: CGSize.init(width: containerWidth, height: CGFloat.greatestFiniteMagnitude),
options: [.usesLineFragmentOrigin, .usesFontLeading],
context: nil)
return ceil(rect.size.height)
}
func width(containerHeight: CGFloat) -> CGFloat {
let rect = self.boundingRect(with: CGSize.init(width: CGFloat.greatestFiniteMagnitude, height: containerHeight),
options: [.usesLineFragmentOrigin, .usesFontLeading],
context: nil)
return ceil(rect.size.width)
}
}
Used like this:
let height = detailPetViewModel!.description.height(containerWidth: Sizes.screenWidth - 40 + 10)

Answer 2

You can simply use (the instance of NSAttributedString).size.height
e.g.
let a = NSAttributedString(string: "A string", attributes: [NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 14)])
let height = a.size().height