How to calculate height of nsattributed string with line spacing dynamically - ios

Question

im trying to calculate the height of a UILabel with LineSpacing attribute. The weird thing is that calculated value of the height of the normal label.text is lower then the label.attributedText with its lineheight. it looks like i'm doing something wrong, but cant find what, so please help :D.
The provided code is specially made for SO to make it compact and clear, it is implemented differently in my project.
extension NSAttributedString {
func heightWithWidth(width: CGFloat) -> CGFloat {
let maxSize = CGSize(width: width, height: CGFloat.max)
let boundingBox = self.boundingRectWithSize(maxSize, options: [.UsesLineFragmentOrigin, .UsesFontLeading, .UsesDeviceMetrics], context: nil)
return boundingBox.height
}
}
extension UILabel {
func getHeightWithGivenWidthAndLineHeight(lineHeight: CGFloat, labelWidth: CGFloat) -> CGFloat {
let text = self.text
if let text = text {
let attributeString = NSMutableAttributedString(string: text)
let style = NSMutableParagraphStyle()
style.lineSpacing = lineHeight
attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
let height = attributeString.heightWithWidth(labelWidth)
self.attributedText = attributeString
return height
}
return 0
}
I call this by
let contentHeight = contentLabel.text! == "" ? 0 : contentLabel.getHeightWithGivenWidthAndLineHeight(3, labelWidth: labelWidth)
Working with normal strings (without spacing) works perfectly, when i use attributedstring with lineSpacing it fails to calculate the correct value.

Answer 1

You can just use UILabel's sizeThatFits. For example:
let text = "This is\nSome\nGreat\nText"
let contentHeight = contentLabel.text! == "" ? 0 : contentLabel.getHeightWidthGivenWidthAndLineHeight(6, labelWidth: labelWidth)
//returns 73.2
But just setting
contentLabel.attributedText = contentLabel.attributedString //attributedString is same as getHeightWidthGivenWidthAndLineHeight
let size = contentLabel.sizeThatFits(contentLabel.frame.size)
//returns (w 49.5,h 99.5)
Code for attributedString added to your extension, if you need to see that:
var attributedString:NSAttributedString?{
if let text = self.text{
let attributeString = NSMutableAttributedString(string: text)
let style = NSMutableParagraphStyle()
style.lineSpacing = 6
attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
return attributeString
}
return nil
}

Answer 2

I updated my Extension this way to set the line height and return the new label height at the same time. Thanx to beyowulf
extension UILabel {
func setLineHeight(lineHeight: CGFloat, labelWidth: CGFloat) -> CGFloat {
let text = self.text
if let text = text {
let attributeString = NSMutableAttributedString(string: text)
let style = NSMutableParagraphStyle()
style.lineSpacing = lineHeight
attributeString.addAttribute(NSParagraphStyleAttributeName, value: style, range: NSMakeRange(0, text.characters.count))
self.attributedText = attributeString
return self.sizeThatFits(CGSize(width: labelWidth, height: 20)).height
}
return 0
}
}