Call API inside powershell function

Question

How to call API inside function. this is my url https://www.gov.uk/bank-holidays.json. I am new for powershell can you help me to do this.

function Holiday {
 
   $list = Invoke-RestMethod -Method Get -Uri https://www.gov.uk/bank-holidays.json
   Write-Host "$list"

}

but i am unable to list . can u please help me on that

Answer 1

Invoke-RestMethod automatically parses the API's JSON response into an object [graph] - a nested [pscustomobject] instance or an array thereof (in a manner of speaking, Invoke-RestMethod has ConvertFrom-Json built in).

While very convenient for subsequent OO processing, the resulting objects' display representation isn't very helpful:

• Only the top-level properties of the object graph are printed.
• Due to a long-standing bug - see GitHub issue #6163 - nested property values may falsely appear to be empty - see this answer for an example.

To quickly visualize the result, you can simply convert back to JSON, using ConvertTo-Json:

function Get-Holiday {
 
  # Call the API, which returns JSON that is parsed into a [pscustomobject]
  # graph, and return (output) the result.
  Invoke-RestMethod -Method Get -Uri https://www.gov.uk/bank-holidays.json

}

$list = Get-Holiday

# Visualize the object for display by converting it back to JSON.
$list | ConvertTo-Json -Depth 3

• Note the unfortunate need to specify -Depth 3 explicitly - see this post for background information.

An alternative visualization can be achieved by piping to Format-Custom:

• The resulting for-display representation isn't JSON, but a notation that resembles hashtable literals and is easy to parse visually.
• Format-Custom's default depth is 5 (compared to ConvertTo-Json's 2), so you will often get away without a -Depth argument.
• Conversely, however, you may need to (temporarily) set the $FormatEnumerationLimit preference variable to ensure that all elements of a collection are visualized; by default, only 4 are, and omitted elements are represented as ….
  That said, if you just want to get a quick sense of the structure of the object graph, that may not be a problem.

# Assumes that $list was obtained as above.
$list | Format-Custom

Output (showing just the first object; note the … indicating that the collection contained in the .events property has additional elements that were omitted):

class PSCustomObject
{
  england-and-wales =
    class PSCustomObject
    {
      division = england-and-wales
      events =
        [
          class PSCustomObject
          {
            title = New Year’s Day
            date = 2018-01-01
            notes =
            bunting = True
          }
          class PSCustomObject
          {
            title = Good Friday
            date = 2018-03-30
            notes =
            bunting = False
          }
          class PSCustomObject
          {
            title = Easter Monday
            date = 2018-04-02
            notes =
            bunting = True
          }
          class PSCustomObject
          {
            title = Early May bank holiday
            date = 2018-05-07
            notes =
            bunting = True
          }
          …
        ]

    }

---

With respect to processing, here's an example that accesses the first entry for England and Wales:

$list.'england-and-wales'.events[0]

The above yields:

title          date       notes bunting
-----          ----       ----- -------
New Year’s Day 2015-01-01          True