@IBDesignable并没有在＆＃34; old＆＃34;项目

Question

我有UIView个子类，例如：

@IBDesignable
class GradientView: UIView {

    @IBInspectable var firstColor: UIColor = UIColor.red
    @IBInspectable var secondColor: UIColor = UIColor.green

    @IBInspectable var vertical: Bool = true

    override func awakeFromNib() {
        super.awakeFromNib()

        applyGradient()
    }

    func applyGradient() {
        let colors = [firstColor.cgColor, secondColor.cgColor]

        let layer = CAGradientLayer()
        layer.colors = colors
        layer.frame = self.bounds
        layer.startPoint = CGPoint(x: 0, y: 0)
        layer.endPoint = vertical ? CGPoint(x: 0, y: 1) : CGPoint(x: 1, y: 0)

        self.layer.addSublayer(layer)
    }

    override func prepareForInterfaceBuilder() {
        super.prepareForInterfaceBuilder()
        applyGradient()
    }
}

它成功地在Interface Builder中呈现了一个新项目，但它并不适用于我的＆＃34; old＆＃34;项目。

有谁知道为什么会这样？