let textLable = UILabel(frame: view.bounds)
textLable.text = "abcd"
textLable.font = .systemFont(ofSize: 500)
textLable.textAlignment = .center
textLable.numberOfLines = 0
view.addSubview(textLable)

動(dòng)態(tài)設(shè)置字體大小

textLable.adjustsFontSizeToFitWidth = true
textLable.minimumScaleFactor = 0.02

獲取字體大小

func adjustedFontSize(label: UILabel) -> CGFloat {
    let text: NSMutableAttributedString = NSMutableAttributedString(attributedString: label.attributedText!)
    text.setAttributes([NSAttributedString.Key.font: label.font as Any], range: NSMakeRange(0, text.length))
    let context: NSStringDrawingContext = NSStringDrawingContext()
    context.minimumScaleFactor = label.minimumScaleFactor
    text.boundingRect(with: label.frame.size, options: NSStringDrawingOptions.usesLineFragmentOrigin, context: context)
    let adjustedFontSize: CGFloat = label.font.pointSize * context.actualScaleFactor
    return adjustedFontSize
}