根据UIlabel IBDesignable中的标题和副标题设置不同的字体

import UIKit

@IBDesignable
class CustomLabel: UILabel {
    
    @IBInspectable var titleFont: UIFont = UIFont.systemFont(ofSize: 16) {
        didSet {
            updateFonts()
        }
    }
    
    @IBInspectable var subtitleFont: UIFont = UIFont.systemFont(ofSize: 12) {
        didSet {
            updateFonts()
        }
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        updateFonts()
    }
    
    override func prepareForInterfaceBuilder() {
        super.prepareForInterfaceBuilder()
        updateFonts()
    }
    
    private func updateFonts() {
        if let text = self.text {
            let attributedText = NSMutableAttributedString(string: text)
            attributedText.addAttribute(.font, value: titleFont, range: NSRange(location: 0, length: text.count))
            
            if let subtitle = self.attributedText?.string {
                attributedText.addAttribute(.font, value: subtitleFont, range: NSRange(location: text.count, length: subtitle.count))
            }
            
            self.attributedText = attributedText
        }
    }
}

let customLabel = CustomLabel()
customLabel.text = "Hello World"
customLabel.titleFont = UIFont.boldSystemFont(ofSize: 20)
customLabel.subtitleFont = UIFont.italicSystemFont(ofSize: 14)