How to save a function into a variable?

Question

How to save a function into a variable?

function sayHello {
    write-host Hello, world!
}

$a = sayHello

Then, I want to call $a.

Another example:

$a = get-childItem
$a -name

Answer 1

You can refer to the function definition itself using the function variable scope qualifier:

$helloFunc = $function:sayHello

Now you can invoke it using the call operator (&):

& $helloFunc

The call operator supports parameters as well:

PS C:\> function test-param {param($a,$b) $b,$a |Write-Host}
PS C:\> $tp = ${function:test-param}
PS C:\> & $tp 123 456
456
123
PS C:\> & $tp -b 123 -a 456
123
456