CODEWITHSUNDEEP
powershellinputscriptingnumbers
peter
peter

Reputation: 73

Check if user input is a number and then select from switch to print

Code:

[int]$s = Read-Host "Enter number from 1-3"
switch ($s) {
  1 { $s = 'Apple' }
  2 { $s = 'Melon' } 
  3 { $s = 'Mango' }
} 
$s

Output:

Cannot convert value "Apple" to type "System.Int32". Error input was not in correct format.

So my question is: How do I check if my input is a number and at the same time select from my switch?

Upvotes: 5

Views: 18313

Answers (5)

Théo Fleury
Théo Fleury

Reputation: 15

function Verify-InputInteger {
    Param (
        $Question="Saisir un nombre",
        $Min=0,
        $Max=100
    )

    try {
        [int]$string_Input = Read-Host $Question;
        
        if($string_Input -LT $Min)
        {
            Throw "ErrorMin"
        }
        if($string_Input -GT $Max)
        {
            Throw "ErrorMax"
        }        
        return $string_Input;
    }
    catch {

        if($_.FullyQualifiedErrorId -EQ 'InvalidCastFromStringToInteger')
        {
            Write-Host 'You did not provide a number as input' -ForegroundColor Red;
            Verify-InputInteger -Question $Question -Min $Min -Max $Max;
        }    
        if($_.Exception.Message -EQ 'ErrorMin')
        {
            Write-Host 'You have entered a number lesser than the minimum limit' -ForegroundColor Red;
            Verify-InputInteger -Question $Question -Min $Min -Max $Max;
        }   
        if($_.Exception.Message -EQ 'ErrorMax')
        {
            Write-Host 'You have entered a number greater than the maximum limit' -ForegroundColor Red;
            Verify-InputInteger -Question $Question -Min $Min -Max $Max;
        }
    }
}

Upvotes: 0

Vivek Kumar Singh
Vivek Kumar Singh

Reputation: 3350

How do I check if my input is a number and at the same time select from my switch?

How do you check if your input is a number? - I think you are already doing that since you are declaring you variable $s as [int] at the very beginning -

[int]$s = Read-Host "Enter number from 1-3"

Selecting from your switch - The error which you are getting is due to the type mismatch of your input to the read-host and the variable $s. $s is clearly an integer where as you are assigning it a string. Hence, the error You have to type-cast that again in order to correct that - 

[int]$s = Read-Host "Enter number from 1-3"
switch ($s) {
1 { [string]$s = 'Apple' }
2 { [string]$s = 'Melon' } 
3 { [string]$s = 'Mango' }
} 
$s

If you enter any number other than 1, 2 or 3, then you $s will store that number in it. For example if you enter 5, $s will store 5 in it since the switch statement hadn't been executed.

Upvotes: 0

Victor Silva
Victor Silva

Reputation: 780

You don't need to use the integer to declare the variable:

$s = Read-Host "Enter number from 1-3"
switch ($s) {
  1 { $s = 'Apple' }
  2 { $s = 'Melon' } 
  3 { $s = 'Mango' }
} 
$s

And if you check the type of variable:

enter image description here

Upvotes: 2

boxdog
boxdog

Reputation: 8442

When you have a predefined set of options like this, consider using a multiple-choice menu, like this:

$title = "Select Fruit"
$prompt = "Which fruit is your favorite?"
$apple = New-Object System.Management.Automation.Host.ChoiceDescription "&Apple","Apple"
$melon= New-Object System.Management.Automation.Host.ChoiceDescription "&Melon","Melon"
$mango= New-Object System.Management.Automation.Host.ChoiceDescription "Man&go", "Mango"

$options = [System.Management.Automation.Host.ChoiceDescription[]]($apple, $melon, $mango)

$selectedFruit = $host.ui.PromptForChoice($title, $prompt, $options, 0) 

switch($selectedFruit)
{
    0 {Write-Host "You chose Apple"}
    1 {Write-Host "You chose Melon"}
    2 {Write-Host "You chose Mango"}
}

In the ISE, the user will see a GUI prompt, with buttons to click on, and at the console, a menu with specific allowed letters to select (A, M and G in this case).

This method has the benefit that it looks like a typical prompt from PowerShell and will check and re-prompt if the user enters an invalid value. You can add a 'quit' option, so the user has an easy way to skip all options.

Upvotes: 1

Mark Wragg
Mark Wragg

Reputation: 23385

The problem with your code is that after you define $s as an integer, you then later try to assign a string value to it.

You could instead do this:

[int]$s = Read-Host "Enter number from 1-3"

$result = switch ($s) {
  1 { 'Apple' }
  2 { 'Melon' } 
  3 { 'Mango' }
} 

$result

Note that i'm also simplifying your code here by returning the result of the switch to $result instead of assigning it inside each condition.

This works because $result is an undefined variable that becomes a string when you assign one to it.

If you want to validate that the input is an integer, you could also consider doing something like this:

$input = Read-Host "Enter number from 1-3"

if (($input -isnot [int])) { Throw 'You did not provide a number as input' }

$result = switch ($input) {
  1 { 'Apple' }
  2 { 'Melon' } 
  3 { 'Mango' }
} 

$result

Upvotes: 4

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