[英]Using Self as generic parameter
I have simple generic class: 我有简单的泛型类:
class MyClass<T> {
let closure: (T -> Void)
init(closure: T -> Void) {
self.closure = closure
}
}
I would like to write an extension for UIView
which would apply closure to any subclass of UIView
: 我想编写一个扩展
UIView
将适用于封闭的任何子类UIView
:
extension UIView {
func apply(c: MyClass<Self>) -> Self {
c.closure(self)
return self
}
}
But it gives me an error: 'Self' is only available in a protocol or as the result of a method in a class
. 但这给了我一个错误:
'Self' is only available in a protocol or as the result of a method in a class
。
Is there any solution to fix this code? 有解决此代码的解决方案吗?
You can achieve this by creating a protocol that UIView and in turn all subclasses will adopt: 您可以通过创建UIView以及所有子类依次采用的协议来实现此目的:
protocol View {}
extension UIView:View {}
extension View {
func apply(c:MyClass<Self>) -> Self {
c.closure(self)
return self
}
}
let m = MyClass<UILabel>(closure: {t in})
let l = UILabel().apply(m) // UILabel returned
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