Checking for bound parameters
I recently read an email where someone was asking how they could check in their function if a value had been provided to one of the parameters. Consider for example,
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function foo
{
param(
$x
)
#If $x was given a value do something, else do something else.
} |
The usual way I’ve seen people deal this problem is by providing a default value which gets assigned to $x in the case that a value wasn’t provided by the caller and then checking for that value.
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function foo
{
param(
$x = $null
)
# Check for $x being null.
} |
That works in the majority of cases, but let’s say that you wanted to differentiate between a default $null value and $null being passed by the caller. What would you do?
If you’re on v2, a simple solution is to look at $PSBoundParameters. It’s a hashtable containing the parameters that were bound and what values were bound to them. Try this:
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function foo
{
param(
$x,
$y
)
$PSBoundParameters
} |
PS >foo 1
Key Value
--- -----
x 1
PS >foo 1 'foo'
Key Value
--- -----
x 1
y foo
With $PSBoundParameters containing all the bound parameters, to check if a parameter was given a value, it’s a simple matter of checking if $PSBoundParameters contains a key for it.
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function foo
{
param(
$x
)
if ($PSBoundParameters.ContainsKey('x'))
{
write-host 'X Bound!'
}
}
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- Marcel Ortiz Soto [MSFT]
