Figure out size of UILabel based on String in Swift

Use an extension on String

Swift 3

extension String {    func height(withConstrainedWidth width: CGFloat, font: UIFont) -> CGFloat {        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)            return ceil(boundingBox.height)    }    func width(withConstrainedHeight height: CGFloat, font: UIFont) -> CGFloat {        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)        return ceil(boundingBox.width)    }}

and also on NSAttributedString (which is very useful at times)

extension NSAttributedString {    func height(withConstrainedWidth width: CGFloat) -> CGFloat {        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)        let boundingBox = boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, context: nil)            return ceil(boundingBox.height)    }    func width(withConstrainedHeight height: CGFloat) -> CGFloat {        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)        let boundingBox = boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, context: nil)            return ceil(boundingBox.width)    }}

Swift 4 & 5

Just change the value for attributes in the extension String methods

from

[NSFontAttributeName: font]

to

[.font : font]

For multiline text this answer is not working correctly. You can build a different String extension by using UILabel

extension String {func height(constraintedWidth width: CGFloat, font: UIFont) -> CGFloat {    let label =  UILabel(frame: CGRect(x: 0, y: 0, width: width, height: .greatestFiniteMagnitude))    label.numberOfLines = 0    label.text = self    label.font = font    label.sizeToFit()    return label.frame.height }}

The UILabel gets a fixed width and the .numberOfLines is set to 0. By adding the text and calling .sizeToFit() it automatically adjusts to the correct height.

Code is written in Swift 3 🔶🐦

Heres a simple solution thats working for me... similar to some of the others posted, but it doesn't not include the need for calling sizeToFit

Note this is written in Swift 5

let lbl = UILabel()lbl.numberOfLines = 0lbl.font = UIFont.systemFont(ofSize: 12) // make sure you set this correctly lbl.text = "My text that may or may not wrap lines..."let width = 100.0 // the width of the view you are constraint to, keep in mind any applied margins herelet height = lbl.systemLayoutSizeFitting(CGSize(width: width, height: UIView.layoutFittingCompressedSize.height), withHorizontalFittingPriority: .required, verticalFittingPriority: .fittingSizeLevel).height

This handles line wrapping and such. Not the most elegant code, but it gets the job done.