Adding methods with ScriptMethod in PowerShell - Step-by-Step Execution

Concept Flow - Adding methods with ScriptMethod

Create object

↓

Define script block

↓

Add ScriptMethod to object

↓

Call method

↓

Method executes script block

↓

Output result

This flow shows how to create an object, add a ScriptMethod to it, then call that method to run the script block and get the output.

Execution Sample

PowerShell

$obj = New-Object PSObject
$scriptBlock = { "Hello, World!" }
$obj | Add-Member -MemberType ScriptMethod -Name Greet -Value $scriptBlock
$obj.Greet()

Creates an object, adds a ScriptMethod named Greet that returns 'Hello, World!', then calls the method.

Execution Table

Step	Action	Variable State	Output
1	Create new PSObject assigned to $obj	$obj = PSObject (empty)
2	Define script block returning 'Hello, World!'	$scriptBlock = script block
3	Add ScriptMethod 'Greet' to $obj with $scriptBlock	$obj has method Greet
4	Call $obj.Greet()	$obj unchanged	Hello, World!
5	End of script	$obj unchanged

💡 Script ends after calling the ScriptMethod and outputting the result.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
$obj	undefined	PSObject (empty)	PSObject (empty)	PSObject with ScriptMethod Greet	PSObject with ScriptMethod Greet	PSObject with ScriptMethod Greet
$scriptBlock	undefined	undefined	Script block returning 'Hello, World!'	Script block returning 'Hello, World!'	Script block returning 'Hello, World!'	Script block returning 'Hello, World!'

Key Moments - 3 Insights

Why do we use a script block when adding a ScriptMethod?

The script block holds the code that runs when the method is called. See execution_table step 2 and 3 where the script block is defined and then added as a method.

Does adding a ScriptMethod change the object’s existing properties?

No, it only adds a new method. The object’s other properties stay the same. See variable_tracker for $obj before and after adding the method.

What happens when we call the ScriptMethod?

The script block runs and returns its output. See execution_table step 4 where calling $obj.Greet() outputs 'Hello, World!'.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. What does $obj have after adding the ScriptMethod?

A A new property named Greet

B A new method named Greet

C The script block removed

D No changes

💡 Hint

Check the 'Variable State' column at step 3 in the execution_table.

At which step does the script block get defined?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Action' column describing defining the script block.

If we change the script block to return 'Hi!', what will be the output at step 4?

A Hi!

B No output

C Hello, World!

D Error

💡 Hint

The output depends on what the script block returns when the method is called.

Concept Snapshot

Add methods to objects using ScriptMethod.
Define a script block with the method code.
Use Add-Member -MemberType ScriptMethod to add it.
Call the method like a normal function.
The script block runs and returns output.

Full Transcript

This example shows how to add a method to a PowerShell object using ScriptMethod. First, we create a new PSObject and store it in $obj. Then, we define a script block that returns the string 'Hello, World!'. Next, we add this script block as a ScriptMethod named Greet to the $obj using Add-Member. Finally, we call $obj.Greet(), which runs the script block and outputs 'Hello, World!'. The object itself does not change except for having the new method added. This method behaves like a function attached to the object.