为什么我需要在PowerShell脚本中首先编写我的函数？ [英] Why do I need to have my functions written first in my PowerShell script?

问题描述

我有一个脚本，我使用函数来包装代码的部分，让我在指定点移动的部分。

不工作的例子

  $ stepChoice = read-host'你想从哪里开始。
 
 switch（$ stepChoice）
 {
 1 {Step1} 
 2 {Step2} 
 3 {Step3} 
 
} 
 
＃Steps.ps1 
 function Step1 {
'Step 1'
 Step2 
} 
 function Step2 {
'Step 2'
 Step3 
} 
 function Step3 {
'Step 3'
'Done！'
} 
  

错误

这会给我以下错误：

术语Step1不被识别为小命令，功能，脚本文件或可操作程序的名称。检查名称的拼写，或者如果包括路径，请验证路径是否正确，然后重试。

 在C：\Tools\Scripts\functiontest.ps1：7 char：12 
 + 1 { Step1<<<< } 
 + CategoryInfo：ObjectNotFound：（Step1：String）[]，CommandNotFoundException 
 + FullyQualifiedErrorId：CommandNotFoundException * 
  

工作示例

如果我更改其周围的顺序工作正常：

 ＃Steps.ps1 
 function Step1 {
'Step 1'
 Step2 
} 
 Step2 {
'Step 2'
 Step3 
} 
 function Step3 {
'Step 3'
'Done！'
} 
 
 #steps 
 $ stepChoice = read-host'你想从哪里开始。
 
 switch（$ stepChoice）
 {
 1 {Step1} 
 2 {Step2} 
 3 {Step3} 
 
} 
  

为什么？

我猜这是因为PS没有加载函数。

解决方案

重新排序您的脚本

我猜想PowerShell是一个解释器，只是从顶部到底部线性地执行一个脚本（在对脚本进行标记化之后），然后一路评估脚本。如果它还没有得到一个函数的定义，你已经尝试调用该函数，PowerShell将会错误。

这里简单的解决方案是

转发声明

。

即使一些编译语言的行为是这样的 - 最引人注目的是C / C ++ - 并且需要 forward declarations 来解决这个问题。

其他语言（如C＃）在编译期间对代码执行多次传递，因此不需要前向递减。

I have a script that I am utilizing functions to wrap parts of the code that allow me to move through the sections at a specified point. What I have found is that I have to have the functions listed first in the script for it to run correctly.

Non-working example

$stepChoice = read-host 'Where would you like to start.'

switch($stepChoice)
{
    1{Step1}
    2{Step2}
    3{Step3}

}

# Steps.ps1 
function Step1 { 
    'Step 1' 
    Step2 
} 
function Step2 { 
    'Step 2' 
    Step3 
} 
function Step3 { 
    'Step 3' 
    'Done!' 
}

Error

This give me the following error:

The term 'Step1' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

 At C:\Tools\Scripts\functiontest.ps1:7 char:12
  +     1{Step1 <<<< }
  + CategoryInfo          : ObjectNotFound: (Step1:String) [], CommandNotFoundException
  + FullyQualifiedErrorId : CommandNotFoundException*

Working example

If I change the order around it works fine:

# Steps.ps1 
function Step1 { 
    'Step 1' 
    Step2 
} 
function Step2 { 
    'Step 2' 
    Step3 
} 
function Step3 { 
    'Step 3' 
    'Done!' 
}

#steps
$stepChoice = read-host 'Where would you like to start.'

switch($stepChoice)
{
    1{Step1}
    2{Step2}
    3{Step3}

}

Why?

I am guessing that it is because PS is not loading the functions.

Why is this and is there a better way to lay out this code structure?

解决方案

Reorder your script

I'm guessing that PowerShell, being an interpreter, just goes through a script linearly top to bottom, (after tokenizing the script) and evaluates the script along the way. If it hasn't gotten to the definition of a function yet and you're already attempting to invoke that function, PowerShell will error out.

The simple solution here is to move the function definitions before the switch statement -- as you've discovered.

Forward declarations

Even some compiled languages behave this way -- most notably C/C++ -- and require forward declarations to work around this issue.

Other languages like C# do multiple passes over the code during compilation so that forward decls aren't required.

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