How to Pass Function as a Parameter

Tagged: PowerShell

Introduction#

In PowerShell, you can pass function as a parameter to another function. This is similar to capability in other programming languages where you can create Higher-order function through lambda or anonymous function.

Problem#

When working with PowerShell, sometimes you want to pass function as parameter to another function, then you want to invoke the passed function.

Solution#

To pass the function as parameter, you can pass it the same way like passing a value. In this case, the function will be the value. Then, you can invoke the passed function using & (the call operator).

Let’s take a look at some examples.

Passing a Function without Parameters#

You can pass the function by position, name or Script Blocks. In other programming languages, Script Blocks is equivalent to anonymous function or lambda.

function MyFunction {
    Param($param)
    Write-Host "I'm calling: $(& $param)"
}

Function Test {
    "Function Test"
}

MyFunction Test
MyFunction -param Test
MyFunction -param { Test }

Below is the output if we execute above script.

Passing a Function with Parameters#

To pass function with its parameters, you can use args automatic variable to get the arguments of passed function.

function MyFunction {
    Param($param)
    Write-Host "I'm calling: $(& $param @args)"
}

Function Test {
    "Function Test with parameters: $args"
}

MyFunction Test a b
MyFunction -param Test a b
MyFunction -param { Test @args } a b

The last line of code above which is MyFunction -param { Test @args } a b using splatting to pass the arguments stored in the args automatic variable.

Below is the output if we execute above script.

Conclusion#

In order to pass function as parameter, the mechanism is the same with passing a value. You can pass it by the name, position or Script Blocks. If you want to invoke the passed function, you can use call operator (&), and also if you want to pass the function with its arguments you can use args automatic variable.