Question

无论如何在powershell中我有以下脚本

function ReturnTrue()
{
    write-host "ReturnTrue executed!"
    return $true
}

if (ReturnTrue -and ReturnTrue -and ReturnTrue)
{
    write-host "ReturnTrue should have executed 3 times"
}

预期输出是看“ReturnTrue已执行！”打印3次，但只打印一次。 C＃或Java中的类似代码将执行ReturnTrue（）3次。这是什么交易？

Answer 1

好陷阱！这是代码及其在注释中的解释，该函数还显示其参数：

function ReturnTrue()
{
    write-host "ReturnTrue executed with $args!"
    return $true
}

# this invokes ReturnTrue once with arguments: -and ReturnTrue -and ReturnTrue
if (ReturnTrue -and ReturnTrue -and ReturnTrue)
{
    write-host "ReturnTrue should have executed 1 time"
}

# this invokes ReturnTrue 3 times
if ((ReturnTrue) -and (ReturnTrue) -and (ReturnTrue))
{
    write-host "ReturnTrue should have executed 3 times"
}

输出：

ReturnTrue executed with -and ReturnTrue -and ReturnTrue!
ReturnTrue should have executed 1 time
ReturnTrue executed with !
ReturnTrue executed with !
ReturnTrue executed with !
ReturnTrue should have executed 3 times

powershell函数仅在使用-and in if条件多次调用时执行一次

1 个答案: