Question

我只是想知道为什么我在括号中嵌入表达式时会得到两个不同的成员列表，例如： gl -stack。似乎没有括号，表达式被完全评估，结果立即传递给下一个管道组件。但是使用括号，集合中的单个对象将逐个传递，以便为集合中的对象调用Get-Member，而不是集合本身。有关Get-Location -Stack的示例，请参阅以下PowerShell交互。

提前致谢！

PS C:\temp\loc1> pushd
PS C:\temp\loc1> pushd ..\loc2
PS C:\temp\loc2> gl -stack

Path
----
C:\temp\loc1
C:\temp\loc1


PS C:\temp\loc2> gl -stack | gm


   TypeName: System.Management.Automation.PathInfoStack

Name          MemberType Definition
----          ---------- ----------
Clear         Method     System.Void Clear()
Contains      Method     bool Contains(System.Management.Automation.PathInfo...
CopyTo        Method     System.Void CopyTo(System.Management.Automation.Pat...
Equals        Method     bool Equals(System.Object obj)
GetEnumerator Method     System.Collections.Generic.Stack`1+Enumerator[[Syst...
GetHashCode   Method     int GetHashCode()
GetType       Method     type GetType()
Peek          Method     System.Management.Automation.PathInfo Peek()
Pop           Method     System.Management.Automation.PathInfo Pop()
Push          Method     System.Void Push(System.Management.Automation.PathI...
ToArray       Method     System.Management.Automation.PathInfo[] ToArray()
ToString      Method     string ToString()
TrimExcess    Method     System.Void TrimExcess()
Count         Property   System.Int32 Count {get;}
Name          Property   System.String Name {get;}


PS C:\temp\loc2> (gl -stack) | gm


   TypeName: System.Management.Automation.PathInfo

Name         MemberType Definition
----         ---------- ----------
Equals       Method     bool Equals(System.Object obj)
GetHashCode  Method     int GetHashCode()
GetType      Method     type GetType()
ToString     Method     string ToString()
Drive        Property   System.Management.Automation.PSDriveInfo Drive {get;}
Path         Property   System.String Path {get;}
Provider     Property   System.Management.Automation.ProviderInfo Provider {...
ProviderPath Property   System.String ProviderPath {get;}

Answer 1

如您所见，

Get-Location -Stack会返回PathInfoStack个对象。该对象派生自实现ICollection的Stack<T>。将表达式放在()内时，PowerShell会对该表达式求值。如果结果是一个集合，那么它将被迭代并输出。你可以通过这个简单的函数看到相同的东西：

PS> function GetArray() { ,@(1,2,3) }
PS> GetArray | Foreach {$_.GetType().FullName}
System.Object[]
PS> (GetArray) | Foreach {$_.GetType().FullName}
System.Int32
System.Int32
System.Int32

“（gl -stack）”和“gl -stack”之间的区别

1 个答案: