PowerShell中的全局变量和局部变量 [英] Global variables and local variables in PowerShell

问题描述

我有全局变量，想在函数中使用它们.

I have global variables and want to use them within a function.

我不在函数中使用相同名称的局部变量！

I don't use local variables with the same name within the functions!

# Global variables:
$Var1 = @{ .. }
$Var2 = @( .. )
function testing{
    $Var1.keyX = "kjhkjh"
    $Var2[2]   = 6.89768
}

我做到了并且可以正常工作，但是它安全吗?还是我必须使用以下内容?

I do it and it works, but is it safe or do I have to use the following?

$Global:Var1.keyX = "kjhkjh"

推荐答案

在您的函数中，您正在修改哈希表的内容，因此除非您的函数(或函数与函数之间的函数调用者)全局范围)碰巧具有局部变量$ Var1和$ Var2(顺便说一句，您是否不错过$).如果这是您自己的代码，那么我会说保持原样.但是，如果您的代码允许其他人的代码调用您的函数，那么我将使用$global:Var1说明符来确保您正在访问全局变量，并且不会无意中访问正在调用的函数中的同名变量您的功能.

In your function, you are modifying the contents of the hashtable so there is no need to use $global unless your function (or a function caller between your function and global scope) happens to have local variables $Var1 and $Var2 (BTW aren't you missing $). If this is all your own code then I'd say leave it as is. However, if you code allows other folks' code to call your function, then I would use the $global:Var1 specifier to make sure you're accessing the global variable and not inadvertently accessing a variable of the same name within a function that is calling your function.

关于PowerShell中动态作用域的另一件事是，当您为函数中的变量分配值时，该变量恰好是全局变量，例如:

Another thing to know about dynamic scoping in PowerShell is that when you assign a value to variable in a function and that variable happens to be a global e.g.:

$someGlobal = 7
function foo { $someGlobal = 42; $someGlobal }
foo
$someGlobal

PowerShell将对函数内的变量$ someGlobal进行写时复制"操作.如果您的意图是真正修改全局，则可以使用$global:说明符:

PowerShell will do a "copy-on-write" operation on the variable $someGlobal within the function. If your intent was to really modify the global then you would use the $global: specifier:

$someGlobal = 7
function foo { $global:someGlobal = 42; $someGlobal }
foo
$someGlobal

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