假设我们有这 3 个类:
Class BaseClass : System.IComparable
{
[int] $Value
BaseClass([int] $v)
{
$this.Value = $v
}
[int] CompareTo($that)
{
If (-Not($that -is [BaseClass])) {
Throw "Not comparable!!"
}
return $this.Value - $that.Value
}
}
Class SubClassA : BaseClass
{
SubClassA([int] $v) : base($v)
{
}
}
Class SubClassB : BaseClass
{
SubClassB([int] $v) : base($v)
{
}
}
当我们比较以下实例时,此实现效果非常好BaseClass
:
$base1 = [BaseClass]::new(1)
$base2 = [BaseClass]::new(2)
Write-Output ($base1 -lt $base2)
# Output: True
Write-Output ($base1 -gt $base2)
# Output: False
但我找不到比较两个子类的两个实例的方法:
$subA1 = [SubClassA]::new(1)
$subB2 = [SubClassB]::new(2)
Write-Output (([BaseClass]$subA1) -lt ([BaseClass]$subB2))
PowerShell 无法执行此代码,引发此错误:
Impossibile confrontare "SubClassA" con "SubClassB".
Errore:
"Impossibile convertire il valore "SubClassB" di tipo "SubClassB" nel tipo "SubClassA"."
从意大利语翻译成英语,此错误消息听起来像:
Unable to compare "SubClassA" with "SubClassB".
Error:
"Unable to convert the value "SubClassB" of type "SubClassB" to the type "SubClassA"."
为什么会出现这个错误?
我们如何比较一个实例SubClassA
与一个实例SubClassB
就好像它们是两个实例BaseClass
?
PS:输出$PSVersionTable
:
PSVersion 5.1.17134.1
PSEdition Desktop
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
BuildVersion 10.0.17134.1
CLRVersion 4.0.30319.42000
WSManStackVersion 3.0
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1