Pass one of the member as array for JSON in powershell - json

Question

Here is a small Powershell code snippet:
$users = New-Object System.Collections.ArrayList
$userAsJson = '
{
"name" : "abc",
"companies" : ["facebook", "google"]
}'
$user = $userAsJson | ConvertFrom-Json
$null = $users.Add($user)
$users | ConvertTo-Json -Depth 5
It gives me the following expected output:
{
"name": "abc",
"companies": [
"facebook",
"google"
]
}
Now, I'm dynamically trying to create the companies list. I tried all possible things which I can think of. Here is what I have tried:
$company = New-Object System.Collections.ArrayList
$null = $company.Add('facebook')
$null = $company.Add('google')
$b = $company.ToArray()
$users = New-Object System.Collections.ArrayList
$userAsJson = '
{
"name" : "abc",
"companies" : $b
}'
$user = $userAsJson | ConvertFrom-Json
$null = $users.Add($user)
$users | ConvertTo-Json -Depth 5
Can anyone suggest me what is the best way to achieve it?

Answer 1

PowerShell's strength is in staying in the realm objects, until the time comes to interface with the outside world, such as when writing to a file or creating a string representation of these objects.
In your case that means:
# Array of companies; statically constructed here, but creating it
# dynamically works just as well.
$company = (
'facebook',
'google'
)
# Initialize the output collection.
# Note: Creating a [System.Collections.ArrayList] instance is
# advisable for building up *large* arrays *incrementally*.
# For smallish arrays, using regular PowerShell arrays will do; e.g.:
# $users = #() # initialize array
# $users += ... # append to array, but be aware that a *new* array
# is created behind the scenes every time.
$users = New-Object System.Collections.ArrayList
# Add a user based on the $company array defined above as
# a [pscustomobject]
$null = $users.Add(
[pscustomobject] #{
name = 'abc'
companies = $company
}
)
# After all users have been added *as objects*, convert them to JSON.
$users | ConvertTo-Json -Depth 5
The above yields (based on a single object having been added; with more, a JSON array would be output):
{
"name": "abc",
"companies": [
"facebook",
"google"
]
}