具有可选属性的 UIView 扩展

Question

这是我现在的代码：

@objc protocol BaseView {
  @objc optional var header: UILabel { get set }
  @objc optional var footer: UILabel { get set }
}

class ViewWithHeader: UIView, BaseView {
  @IBOutlet var header: UILabel!
}

class ViewWithFooter: UIView, BaseView {
  @IBOutlet var footer: UILabel!
}


var view: BaseView!
if (header != nil) {
  view = Bundle.main.loadNibNamed("ViewWithHeader", owner: self, option: nil)?.first as! ViewWithHeader
} else if (footer != nill) {
  view = Bundle.main.loadNibNamed("ViewWithFooter", owner: self, option: nil)?.first as! ViewWithFooter
}

view.header?.text = "Header"
view.footer?.text = "Footer"
view.alpha // This line fails because BaseView has no member 'alpha'

我的问题是如何扩展 UIView 以包含可选的 header 和 footer 变量？也许我做的完全错了，在这种情况下，我会很感激正确方向的指示。

Answer 1

如果我对你的问题的理解正确，你需要让你的 BaseView 成为 UIView 的子class。然后在您的 class 定义中，您可以根据需要添加可选属性。代码看起来像这样

class BaseView: UIView {
    var header: UILabel?
    var footer: UILabel?
}

编辑

根据您在评论中的解释，我相信您需要这样的东西

class BaseView: UIView {
    @IBOutlet var header: UILabel?
    @IBOutlet var footer: UILabel?
}

class ViewWithHeader: BaseView {
}

class ViewWithFooter: BaseView {
}


var view: BaseView!
if (header != nil) {
  view = Bundle.main.loadNibNamed("ViewWithHeader", owner: self, option: nil)?.first as! ViewWithHeader
} else if (footer != nil) {
  view = Bundle.main.loadNibNamed("ViewWithFooter", owner: self, option: nil)?.first as! ViewWithFooter
}

view.header?.text = "Header"
view.footer?.text = "Footer"
view.alpha // This line fails because BaseView has no member 'alpha'

具有可选属性的 UIView 扩展

UIView extension with optional properties

uiview

swift

swift-extensions