[英]Swift Protocol as Generic Parameter
Given this class: 鉴于此类:
class ServiceRegistry {
var store = [String : AnyObject]()
var allRegisteredType: [String] {
return store.map { $0.0 }
}
func registerInstance<T>(instance:AnyObject, forType type: T.Type) {
store[String(type)] = instance
}
func instanceForType<T>(type: T.Type) -> T? {
return store[String(type)] as? T
}
}
Is there a way I can enforce that T
must be a Protocol, without using the @obj? 有没有办法我可以强制执行T
必须是一个协议,而不使用@obj?
This is a modified version of my type assertion technique. 这是我的类型断言技术的修改版本。 I added the "as? AnyClass" assert so that the type can only be of protocol type. 我添加了“as?AnyClass”断言,因此类型只能是协议类型。 There might be a more elegant way of doing this but going through my notes and research about class assertion this is what I came up with. 可能有一种更优雅的方式来做这个,但通过我的笔记和关于类断言的研究,这就是我提出的。
import Foundation
protocol IDescribable:class{}
class A:IDescribable{}
class B:A{}
let a = A()
let b = B()
func ofType<T>(instance:Any?,_ type:T.Type) -> T?{/*<--we use the ? char so that it can also return a nil*/
if(instance as? T != nil && type as? AnyClass == nil){return instance as? T}
return nil
}
Swift.print(ofType(a,A.self))//nil
Swift.print(ofType(a,IDescribable.self))//A
Swift.print(ofType(b,B.self))//nil
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