Objects

Everything in PowerShell is an object. An object is a combination of variables and functions. Each object has:

• Properties: Variables that describe the object (characteristics).
• Methods: Functions that define how to use the object (actions).

Each object is an instance of a blueprint called a type, or class.

Getting Properties and Methods of an Object

All information associated with an object is called a member. The Get-Member cmdlet reveals the members of an object, such as properties and methods. It also shows the type of an object.

"Codecademy" | Get-Member

Object Properties

Properties are also called attributes and are characteristics of an object. The Get-Member cmdlet can be utilized with the MemberType parameter to only show the properties of an object. Consider a String object as an example:

PS > $my_string = "Codecademy"
PS > $my_string | Get-Member -MemberType Property # Shows all properties of the String object

  TypeName: System.String

Name   MemberType Definition
----   ---------- ----------
Length Property   int Length {get;}

String objects have a property called Length, which holds the number of characters in a string.

PS > $my_string.Length # "Codecademy" has 10 characters
10

Object Methods

Methods are the actions an object can take. One of the methods of a String object, for example, is Contains(). This method returns True if a string contains the specified substring, otherwise False.

PS > $my_string.Contains("Code")
True

The MemberType parameter of the Get-Member cmdlet can be modified to show only the methods of an object.

# Shows all methods of the String object
$my_string | Get-Member -MemberType Method

Creating a Custom Object

PowerShell allows the creation of custom objects. To create a custom object called dog, we use the New-Object cmdlet with the PSCustomObject type name.

$dog = New-Object -TypeName PSCustomObject

By default, new custom objects have no properties and four methods.

PS > $dog | Get-Member
  TypeName: System.Management.Automation.PSCustomObject

Name        MemberType Definition
----        ---------- ----------
Equals      Method     bool Equals(System.Object obj)
GetHashCode Method     int GetHashCode()
GetType     Method     type GetType()
ToString    Method     string ToString()

Adding Properties

To add properties to custom objects, use the Add-Member cmdlet. A type of member must be specified using the -MemberType parameter. For a simple key-value pair, we use NoteProperty but there is also AliasProperty, CodeProperty, and ScriptProperty.

$dog | Add-Member -MemberType NoteProperty -Name "DogName" -Value "Rufus"

-Name is used to specify the name of the property and -Value is used to specify the value to be assigned.

Adding Methods

Adding methods to custom objects is similar to adding properties but ScriptMethod is specified for the MemberType parameter. A piece of code encapsulated within curly braces { } called ScriptBlock is also needed.

In the example below, a script block called speak is first defined and then added as a method to the dog custom object.

$speak = {
    "Woof!"
}

$dog | Add-Member -MemberType ScriptMethod -Name "speak" -Value $speak

Using a Hashtable

An alternative method to creating a custom object is by utilizing a hashtable. A hashtable defines multiple key-value pairs which can be used to easily add properties to a custom object.

# Creates a custom object called dog
$dog = [PSCustomObject]@{
    # Adds a Name property with "Rufus" as its value
    Name = "Rufus"

    # Adds an Age property with 10 as its value
    Age = 10
}