在swift中获取泛型的参数化类型？

问题描述

如何在swift中获得泛型的参数化类型？例如，检查类型的大小。

解决方案

例如，当您有 Array< ; Int> value，你想要的是 Int type。

我相信是没有通用的方式来做到这一点。

某些类型具有 typealias ed通用参数，您可以通过那个名字。例如：

  let array：Array< UInt16> = [1,2,3] 
 let elementType = array.dynamicType.Element.self //  - > Swift.UInt16 
 sizeof（elementType）//  - > 2 
  

这是因为 Array typealiased Element = T ：

  struct Array< T> ：MutableCollectionType，Sliceable，_DestructorSafeContainer {
 
 ///这个`Array`存储的元素的类型
 typealias Element = T 
   typealias ，你可以通过扩展名添加它
 
 
 
 / code>：
 扩展非托管{
 typealias Payload = T 
} 
 
让某些东西：非托管< NSString> = .passRetained（test）
 something.dynamicType.Payload.self //  - > NSString 
  
 
How can I get the parameterised type of a generic in swift? For example to check the sizeof the type.
 解决方案 
I suppose, for example, when you have Array<Int> value, what you want is Int type.
I believe there is no generic way to do that.
Some type has typealiased the generic parameter, you can get it with that name. For example:
let array: Array<UInt16> = [1,2,3]
let elementType = array.dynamicType.Element.self // -> Swift.UInt16
sizeof(elementType) // -> 2
This works because Array typealiased Element = T:
struct Array<T> : MutableCollectionType, Sliceable, _DestructorSafeContainer {

    /// The type of element stored by this `Array`
    typealias Element = T
Even if it does not have the typealias, you can add it by extension:
extension Unmanaged {
    typealias Payload = T
}

let something: Unmanaged<NSString> = .passRetained("test")
something.dynamicType.Payload.self // -> NSString
                        
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