为什么'$true -eq“字符串"'返回 $true? [英] Why does '$true -eq "string"' returns $true?

问题描述

在 powerShell 中，您使用-eq"运算符将布尔值与字符串进行比较，它总是会返回与我之前比较时相同的布尔值.

In powerShell you compare a boolean with a string with the "-eq" operator it will always return the same boolean as I used to compare.

例如

$shouldBeFalse = $true -eq "hello"
$shouldBeTrue = $false -eq "hello"

变量 $shouldBeFalse 是 $true.变量 $shouldBeTrue 是 $false.

The variable $shouldBeFalse is $true. The variable $shouldBeTrue is $false.

我不得不使用Equals"方法:

I had to use the "Equals" method:

$shouldBeFalse = $true.Equals("hello")

在这种情况下，$shouldBeFalse 是 $false.

In this case $shouldBeFalse is $false.

但是为什么会返回带有布尔值的 -eq 运算符呢?

But why returns the -eq operator with boolean these kind of results?

推荐答案

PowerShell 将始终使用左侧参数的类型进行评估.由于左侧有一个布尔值，PowerShell 将尝试将Hello"转换为布尔值，以便使用 -eq 进行评估.

PowerShell will always evaluate using the type of the left-side argument. Since you have a boolean on the left PowerShell will try and cast "Hello" as a boolean for the purpose of evaluating with -eq.

因此，在您的情况下， "hello" 被转换为布尔值 [bool]"hello" ，因为它不是零长度字符串，所以它的计算结果为 True.如果你反其道而行之，你会看到类似的行为.

So in your case "hello" is converted to a boolean value [bool]"hello" which would evaluate to True since it is not a zero length string. You would see similar behavior if you did the opposite.

PS C:> "hello" -eq $true
False

PS C:> [bool]"hello" -eq $true
True

在第一种情况下，$true 被转换为字符串true"，它不等于hello"，因此为 false.在第二种情况下，我们将hello"转换为布尔值，因此 -eq 将比较布尔值.由于提到的原因，这评估为 True.

In the first case $true is converted to a string "true" which does not equal "hello" hence false. In the second case we cast "hello" to boolean so the -eq will compare boolean values. For reasons mentioned about this evaluates to True.

另一个很好的解释来自这个答案，它可能会将您的问题标记为重复:为什么是 $false -eq """真的吗?

Another good explanation comes from this answer which might get your question flagged as a duplicate: Why is $false -eq "" true?

这篇关于为什么'$true -eq“字符串"'返回 $true?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！