我正在构建简单的主题引擎,并希望有一个扩展,将UISwipeGestureRecognizer添加到UIViewController
这是我的代码：
protocol Themeable {
func themeDidUpdate(currentTheme: Theme) -> Void
}
extension Themeable where Self: UIViewController {
func switchCurrentTheme() {
Theme.switchTheme()
themeDidUpdate(Theme.currentTheme)
}
func addSwitchThemeGestureRecognizer() {
let gestureRecognizer = UISwipeGestureRecognizer(target: self,action:#selector(Self.switchCurrentTheme))
gestureRecognizer.direction = .Down
gestureRecognizer.numberOfTouchesrequired = 2
self.view.addGestureRecognizer(gestureRecognizer)
}
}
当然编译器找不到#selector(Self.switchCurrentTheme),因为它没有通过@objc指令公开.是否可以将此行为添加到我的扩展程序？
解决方法
我能想到的最干净,最有效的解决方案是使用相关方法在UIViewController上定义一个私有扩展.通过将范围限制为私有,对此方法的访问被隔离到定义协议的源文件中.这是它的样子：
protocol Themeable {
func themeDidUpdate(currentTheme: Theme) -> Void
}
fileprivate extension UIViewController {
@objc func switchCurrentTheme() {
guard let themeableSelf = self as? Themeable else {
return
}
Theme.switchTheme()
themeableSelf.themeDidUpdate(Theme.currentTheme)
}
}
extension Themeable where Self: UIViewController {
func addSwitchThemeGestureRecognizer() {
let gestureRecognizer = UISwipeGestureRecognizer(target: self,action:#selector(switchCurrentTheme))
gestureRecognizer.direction = .Down
gestureRecognizer.numberOfTouchesrequired = 2
self.view.addGestureRecognizer(gestureRecognizer)
}
}
