CODEWITHSUNDEEP
functionpowershell
CharlieShi
CharlieShi

Reputation: 916

How to call powershell function properly?

I wrote a function to convert the input month parameter to a certain format. such as if I passed 04 to the function and the function will return the "_APR_". the function I wrote is like below:

function GetEnMonth()
{
param([string] $month)
switch ($month)
{
    ($_ -eq "01"){$result = "_JAN_"}
    ($_ -eq "02"){$result = "_FEB_"}
    ($_ -eq "03"){$result = "_MAR_"}
    ($_ -eq "04"){$result = "_APR_"}
    ($_ -eq "05"){$result = "_MAY_"}
    ($_ -eq "06"){$result = "_JUN_"}
    ($_ -eq "07"){$result = "_JUL_"}
    ($_ -eq "08"){$result = "_AUG_"}
    ($_ -eq "09"){$result = "_SEP_"}
    ($_ -eq "10"){$result = "_OCT_"}
    ($_ -eq "11"){$result = "_NOV_"}
    ($_ -eq "12"){$result = "_DEC_"}
    default {$result ="_No_Result_"}
}
return [string]$result;
}

Then I use below command to execute the function to get the result:

$mYear = $today.substring(0,4) 
$mMonth =$today.substring(4,2)
$mDate = $today.substring(6,2)
$monthInEn = GetEnMonth $mMonth

well, the result is always "_No_Result_", why? below is the exception:

 **** Exception type : System.Management.Automation.RuntimeException
 **** Exception message : You cannot call a method on a null-valued expression.

Could anyone give me an answer for this? I have searched Google a lot but don't find useful solutions.

Upvotes: 1

Views: 2688

Answers (4)

Shay Levy
Shay Levy

Reputation: 126712

Here's my take on this. I changed the parameter type to Int, with this you'll be able to get process such as "03" or 3. I also added break statements to make the switch work faster.

function GetEnMonth
{
    param([int] $month)

    switch ($month)
    {
        1 {"_JAN_"; break}
        2 {"_FEB_"; break}
        3 {"_MAR_"; break}
        4 {"_APR_"; break}
        5 {"_MAY_"; break}
        6 {"_JUN_"; break}
        7 {"_JUL_"; break}
        8 {"_AUG_"; break}
        9 {"_SEP_"; break}
        10 {"_OCT_"; break}
        11 {"_NOV_"; break}
        12 {"_DEC_"; break}
        default {"_No_Result_"}
    }
}

Upvotes: 3

JPBlanc
JPBlanc

Reputation: 72610

This is not an answer, but another way to do the same in one line and with a culture param:

$month = 3
$smonth=[string]::format([System.Globalization.CultureInfo]"en-US", "_{0:MMM}_",[datetime]("$month/01"))
$smonth
_MAR_

Upvotes: 2

CB.
CB.

Reputation: 60910

Your switch statment is wrong try this:

function GetEnMonth()
{
param([string] $month)
switch ($month)
{
    "01" {$result = "_JAN_"}
    "02" {$result = "_FEB_"}
    "03" {$result = "_MAR_"}
    "04" {$result = "_APR_"}
    "05" {$result = "_MAY_"}
    "06" {$result = "_JUN_"}
    "07" {$result = "_JUL_"}
    "08" {$result = "_AUG_"}
    "09" {$result = "_SEP_"}
    "10" {$result = "_OCT_"}
    "11" {$result = "_NOV_"}
    "12" {$result = "_DEC_"}
    default {$result ="_No_Result_"}
}
return [string]$result;
}

Upvotes: 2

jon Z
jon Z

Reputation: 16616

This should work:

function GetEnMonth
{
param([string] $month)
switch ($month)
{
    "01"{$result = "_JAN_"}
    "02"{$result = "_FEB_"}
    "03"{$result = "_MAR_"}
    "04"{$result = "_APR_"}
    "05"{$result = "_MAY_"}
    "06"{$result = "_JUN_"}
    "07"{$result = "_JUL_"}
    "08"{$result = "_AUG_"}
    "09"{$result = "_SEP_"}
    "10"{$result = "_OCT_"}
    "11"{$result = "_NOV_"}
    "12"{$result = "_DEC_"}
    default {$result ="_No_Result_"}
}
return [string]$result;
}

Upvotes: 3

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