In Powershell what is the idiomatic way of converting a string to an int?
PowershellPowershell Problem Overview
The only method I have found is a direct cast:
> $numberAsString = "10"
> [int]$numberAsString
10
Is this the standard approach in Powershell? Is it expected that a test will be done before to ensure that the conversion will succeed and if so how?
Powershell Solutions
Solution 1 - Powershell
You can use the -as operator. If casting succeed you get back a number:
$numberAsString -as [int]
Solution 2 - Powershell
Using .net
[int]$b = $null #used after as refence
$b
0
[int32]::TryParse($a , [ref]$b ) # test if is possible to cast and put parsed value in reference variable
True
$b
10
$b.gettype()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True Int32 System.ValueType
note this (powershell coercing feature)
$a = "10"
$a + 1 #second value is evaluated as [string]
101
11 + $a # second value is evaluated as [int]
21
Solution 3 - Powershell
A quick true/false test of whether it will cast to [int]
[bool]($var -as [int] -is [int])
Solution 4 - Powershell
For me $numberAsString -as [int] of @Shay Levy is the best practice, I also use [type]::Parse(...) or [type]::TryParse(...)
But, depending on what you need you can just put a string containing a number on the right of an arithmetic operator with a int on the left the result will be an Int32:
PS > $b = "10"
PS > $a = 0 + $b
PS > $a.gettype()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True Int32 System.ValueType
You can use Exception (try/parse) to behave in case of Problem
Solution 5 - Powershell
I'd probably do something like that :
[int]::Parse("35")
But I'm not really a Powershell guy. It uses the static Parse method from System.Int32. It should throw an exception if the string can't be parsed.
Solution 6 - Powershell
Building up on Shavy Levy answer:
[bool]($var -as [int])
Because $null is evaluated to false (in bool), this statement Will give you true or false depending if the casting succeeds or not.
Solution 7 - Powershell
$source = "number35"
$number=$null
$result = foreach ($_ in $source.ToCharArray()){$digit="0123456789".IndexOf($\_,0);if($digit -ne -1){$number +=$\_}}[int32]$number
Just feed it digits and it wil convert to an Int32