Set method as property of object in Powershell - powershell

Question

I have an array of objects like this
$all = #(
#{ Name = 'First'; Method = { FirstMethod 1 }; Description = "First Description"; }
#{ Name = 'Second'; Description = "Second Description" }
#{ Name = 'Third'; Method = { ThirdMethod }; Description = "Third Description" }
)
Which every obeject has a Name (string), a Description (string), and a Method (which contains a function and its optional)
While the FirstMethod and SecondMethod looks like this:
Function FirstMethod
{
param($number)
Write-Host "$number - some other things"
return $number
}
Function ThirdMethod
{
Write-Host "Second called"
return 'test'
}
And I am iterating through all the items in $all and trying to call Method parameter if it exists:
Function RunAll
{
foreach($item in $all)
{
If($item.Method)
{
Write-Host "It has method and its running it"
$returned_from_method = $item.Method
Write-Host "Value returned from method: $returned_from_method"
}
Else
{
Write-Host "Does not have a method!"
}
}
}
So basically what I need here is that: when the loop is in the First item in array $returned_from_method = $item.Method it should return 1 (because it calls FirstMethod and passes 1. And when the loop is in the Third item in array it should return test (because it calls ThirdMethod).
Is there anyway I can achieve this?

Answer 1

The code you posted does neither define (custom) objects nor methods. It defines a list of hashtables where one key has a scriptblock value. Using dot-access on that key will just return the definition of the scriptblock, not invoke it.
Demonstration:
PS C:\> $ht = #{Name='foo'; Method={FirstMethod 1}; Description='bar'}
PS C:\> $ht.Method
FirstMethod 1
Even if you convert the hashtable to an object, that behavior does not change:
PS C:\> $obj = [PSCustomObject]$ht
PS C:\> $obj.Method
FirstMethod 1
To actually invoke the scriptblock you need to call the scriptblock's Invoke() method:
PS C:\> $ht.Method.Invoke()
1 - some other things
1
PS C:\> $obj.Method.Invoke()
1 - some other things
1
Whether the function called in the scriptblock is defined before or after creation of the hashtable or object doesn't matter, as long as it is defined before the scriptblock is invoked. The code in your own answer seems to work only because you replaced the scriptblock (curly brackets) with a grouping expression (parentheses). That means, however, that the "method" is evaluated upon definition of the hashtable and only the return value of the function is stored with the key. The Write-Host output is written to the console immediately and not stored with the key.
PS C:\> $ht = #{Name='foo'; Method=(FirstMethod 1); Description='bar'}
1 - some other things
PS C:\> $ht.Method
1
For creating an object with an actual (script)method you need to add a property with the correct type:
PS C:\> $obj | Add-Member -Name 'Method2' -Type ScriptMethod -Value {FirstMethod 2}
PS C:\> $obj.Method2()
2 - some other things
2
The code for creating your objects should thus look somewhat like this:
$obj1 = [PSCustomObject]#{
Name = 'First'
Description = 'First Description'
}
$obj1 | Add-Member -Name 'Method' -Type ScriptMethod -Value {FirstMethod 1}
$obj2 = [PSCustomObject]#{
Name = 'Second'
Description = 'Second Description'
}
$obj3 = [PSCustomObject]#{
Name = 'Third'
Description = 'Third Description'
}
$obj3 | Add-Member -Name 'Method' -Type ScriptMethod -Value {ThirdMethod}
$all = $obj1, $obj2, $obj3

Answer 2

If anyone is struggling with this one here's the answer:
The methods FirstMethod and ThirdMethod should be declared before the array
and then i needed to add the function inside (), and not {}.
Function FirstMethod
{
param($number)
Write-Host "$number - some other things"
return $number
}
Function ThirdMethod
{
Write-Host "Second called"
return 'test'
}
$all = #(
#{ Name = 'First'; Method = ( FirstMethod 1 ); Description = "First Description"; }
#{ Name = 'Second'; Description = "Second Description" }
#{ Name = 'Third'; Method = ( ThirdMethod ); Description = "Third Description" }
)
And it works fine now!