How to use custom TextStyle in xib?

In code , I can define a UILabel has a dynamic font like this, and I change this body TextStyle font from default size to 30.

label.font = UIFontMetrics(forTextStyle: .body).scaledFont(for: UIFont.systemFont(ofSize: 30))

But in Xib , I can only use the default body TextStyle . Is there any way to change body TextStyle 's default configuration in xib?

You can achieve this with a custom label. I will use @IBDesignable and @IBInspectable to update the UI.

1. Create your own custom label:

@IBDesignable
class BodyTextStyleLabel: UILabel {
    @IBInspectable var bodyTextStyleFontSize: CGFloat = 30 {
        didSet {
            //Default is .body as you mentioned
            self.font = UIFontMetrics(forTextStyle: .body)
                .scaledFont(for: .systemFont(ofSize: bodyTextStyleFontSize))
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    private func setup() {
        bodyTextStyleFontSize = 30
    }
}

2. In XIB file, change your default label to the class that is defined above and the expected font size: