Pass function as a parameter

Question

I've written function 'A' that will call one of a number of other functions. To save re-writing function 'A', I'd like to pass the function to be called as a parameter of function 'A'. For example:

function A{
    Param($functionToCall)
    Write-Host "I'm calling : $functionToCall"
}

function B{
    Write-Host "Function B"
}

Function C{
    write-host "Function C"
}

A -functionToCall C

Returns: I'm calling: C

I am expecting it to return: I'm calling: Function C.

I've tried various things such as:

Param([scriptblock]$functionToCall)

Cannot convert System.String to ScriptBlock

A -functionToCall $function:C

Returns "Write-Host "Function C"

A - functionToCall (&C)

This evaluates before the rest of it:

 Function C
 I'm Calling :

I'm sure this is programming 101, but I can't work out the correct syntax or what it is I'm doing wrong.

Answer 1

I'm not sure this is the best, but:

function A{
    Param([scriptblock]$FunctionToCall)
    Write-Host "I'm calling $($FunctionToCall.Invoke(4))"
}

function B($x){
    Write-Output "Function B with $x"
}

Function C{
    Param($x)
    Write-Output "Function C with $x"
}

PS C:\WINDOWS\system32> A -FunctionToCall $function:B
I'm calling Function B with 4

PS C:\WINDOWS\system32> A -FunctionToCall $function:C
I'm calling Function C with 4

PS C:\WINDOWS\system32> A -FunctionToCall { Param($x) "Got $x" }
I'm calling Got x