似乎无法将泛型集合与 PowerShell 类一起使用 [英] Can't seem to use generic collection with a PowerShell class

问题描述

我正在尝试调用 List[T](IEnumerable) 像这样直接将一个项目添加到初始的List，其中T 是我编写的 PowerShell 类(以下示例使用类名 Thing:

I'm trying to invoke the List[T](IEnumerable) directly adding an item to the initial List like so, where T is a PowerShell class I've written (the below example uses the class name Thing:

$someObject = Get-Thing # returns a single object
$list = [List[Thing]]::new(@( $someObject ))

然而，这会产生一个错误，表明它找不到这个构造函数的重载:

However, this yields an error suggesting it can't find the overload for this constructor:

找不到List`1"的重载；和参数计数:1".

Cannot find an overload for "List`1" and the argument count: "1".

将 List[T] 设置为 Object 类有效，但是:

Setting List[T] to the Object class works, however:

$someObject = Get-Thing
$list = [List[Object]]::new(@( $someObject ))

虽然这有效，但我不确定为什么我无法使用我的 PowerShell 类作为类型.我的理解是 仅上下文-绑定类型和(默认情况下)嵌套类型 不能与泛型一起使用，但以下显示我的类不是 ContextBoundObject:

While this works, I'm unsure why I'm unable to use my PowerShell class as the type. My understanding is that only context-bound types and (by default) nested types are unable to be used with generics, but the following shows that my class is not a ContextBoundObject:

class Thing {
  $Name

  Thing($name) {
    $this.Name = $name
  }
}
$thing = [Thing]::new('Bender')
$thing -is [System.ContextBoundObject] # ==> False

我不确定 PowerShell 类是否是某种嵌套类型，并且 about_Classes 没有提到嵌套类型.

I'm not certain if a PowerShell class would be a nested type of some sort, and about_Classes does not mention nested types.

推荐答案

我不确定为什么我不能使用我的 PowerShell 类作为类型

I'm unsure why I'm unable to use my PowerShell class as the type

数组子表达式运算符 @() 返回其结果为 [object[]] - 满足参数类型 [IEnumerable[object]] 的类型 - 这就是为什么当您使用 [object] 作为接收集合类型的类型参数时它总是有效的原因.

The array subexpression operator @() returns its results as [object[]] - a type which satisfies the argument type [IEnumerable[object]] - which is why it always works when you use [object] as the type parameter for the receiving collection type.

那么，该怎么办?

如果数组仅由 [Thing] 组成，您可以显式转换为实现 [IEnumerable[Thing]] 的更具体的集合类型:

If the array consists only of [Thing]'s, you can explicitly cast to a more specific collection type that implements [IEnumerable[Thing]]:

$list = [List[Thing]]::new([Thing[]]@( $someObject ))

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