Swift How to calculate one line text height from its font - ios

Question

I ran into an issue where I needed to animate translating a label vertically the same distance of a textField's text height. In most cases just textField.bounds.heigt but if the textField's height is bigger than the text height it will not be any good for me. So I need to know:
How to calculate the line height of the string text from its UIFont?
Regarding the duplicate:
There's a little bit different of what I need. that answer(which I've referenced in my answer) get the total height depending on 1) the string 2) the width 3) the font. What I needed is one line height dpending only on the font.

Answer 1

UIFont has a property lineHeight:
if let font = _textView.font {
let height = font.lineHeight
}
where font is your font

Answer 2

I have been searching for a way to do that and find this answer where it has a String extension to calculate the size for the string and a given font. I have modified it to do what I want (get the line height of text written using a font.):
extension UIFont {
func calculateHeight(text: String, width: CGFloat) -> CGFloat {
let constraintRect = CGSize(width: width, height: CGFloat.greatestFiniteMagnitude)
let boundingBox = text.boundingRect(with: constraintRect,
options: NSStringDrawingOptions.usesLineFragmentOrigin,
attributes: [NSAttributedStringKey.font: self],
context: nil)
return boundingBox.height
}
}
I hope this helps someone looking for it. (may be myself in the future).

Answer 3

I've used this String extension in the past to draw some text as opposed to creating a UILabel somewhere. I don't like the fact that I can't seem to get the real height of the specific text I want to draw (not every string contains capital letters or characters with descenders, etc.) I've used a couple of enums for horizontal and vertical alignment around the given point. Open to ideas on the vertical height.
public func draw(at pt: CGPoint,
font: UIFont? = UIFont.systemFont(ofSize: 12),
color: UIColor? = .black,
align: HorizontalAlignment? = .Center,
vAlign: VerticalAlignment? = .Middle)
{
let attributes: [NSAttributedString.Key : Any] = [.font: font!,
.foregroundColor: color!]
let size = self.boundingRect(with: CGSize(width: 0, height: 0),
options: [ .usesFontLeading ],
attributes: [ .font: font! ],
context: nil).size
var x = pt.x
var y = pt.y
if align == .Center {
x -= (size.width / 2)
} else if align == .Right {
x -= size.width
}
if vAlign == .Middle {
y -= (size.height / 2)
} else if vAlign == .Bottom {
y -= size.height
}
let rect = CGRect(x: x, y: y, width: size.width, height: size.height)
draw(in: rect, withAttributes: attributes)
}