Nested arrays and ConvertTo-Json

Question

To use a REST API, I must pass a JSON object that looks like this:

{ "series" : 
  [{  
      "metric": "custom.powershell.gauge",
      "points":[[1434684739, 1000]]
    }
  ]
}

Note the nested array here. I cannot get to reproduce this. Here is my code:

[int][double]$unixtime=get-date ( (get-date).ToUniversalTime() ) -UFormat %s
$obj=@{}
$series=@{}
$array=@()
$points=@()
$value=get-random -Minimum 0 -Maximum 100


$series.add("metric","custom.powershell.gauge")
$points=@(@($unixtime, $value))
$series.add("points",$points)
$obj.Add("series",@($series))

$json=$obj | ConvertTo-Json -Depth 30 -Compress
$json

And here is the output:

{"series":[{"points":[1434685292,95],"metric":"custom.powershell.gauge"}]}

I've tried many things, I cannot get the 2 arrays to be nested, it always end up looking like a single array.

On the same note, came someone explain this please:

> $a=(1,2)
> $a
1
2
> $a | ConvertTo-Json
[
    1,
    2
]
> $b=($a,$a)
> $b
1
2
1
2
> $b | ConvertTo-Json
[
    {
        "value":  [
                      1,
                      2
                  ],
        "Count":  2
    },
    {
        "value":  [
                      1,
                      2
                  ],
        "Count":  2
    }
]

Where are these value and Count coming from?

Thanks for your help.

Answer 1

The explanation is that (1,2),(3,4) is an array of array, but Powershell split the first level with the pipe |, and you don't give a name for these arrays so the serializer supplies it. First have a try to this :

# First build your array of array
$z = (1,2),(3,4)
# convert it to JSON using the ,
,$z | ConvertTo-Json -Depth 5 -Compress
[psobject]@{"points"=$z} | ConvertTo-Json -Depth 5 -Compress

It gives the first step:

{"value":[[1,2],[3,4]],"Count":2}
{"points":[[1,2],[3,4]]}

Now the solution I propose :

# First build your array of array
$z = (1,2),(3,4)

# Then build a PSCustom object
$a = [pscustomobject]@{"series" = ,@{"metric"="custom.powershell.gauge"; "points"=$z}}

# At the end convert it to JSON
# don't forget the **Depth** parameter (use **Compress** to retreive one line like above)
$a | ConvertTo-Json -Depth 5

For me it gives something close to what you need:

{
    "series":  [
                   {
                       "points":  [
                                      [
                                          1,
                                          2
                                      ],
                                      [
                                          3,
                                          4
                                      ]
                                  ],
                       "metric":  "custom.powershell.gauge"
                   }
               ]
}

Answer 2

Late to the party, but I'd like to propose a more visually intuitive solution that's easy to expand (I, like others, am a visual learner so code blocks like the below help me understand things more easily):

[int][double]$unixtime = Get-Date ((Get-Date).ToUniversalTime()) -UFormat %s
$value = Get-Random -Minimum 0 -Maximum 100
$body = @{
    'series' = @(
        [Ordered]@{
            'metric'='custom.powershell.gauge'
            'points' = @(
                ,@($unixtime,$value)
            )
        }
    )  
}
ConvertTo-Json -InputObject $body -Depth 4

Outputs:

{
    "series":  [
                   {
                       "metric":  "custom.powershell.gauge",
                       "points":  [
                                      [
                                          1473698742,
                                          96
                                      ]
                                  ]
                   }
               ]
}

-Depth 4 gets you the additional set of square brackets around your point values, and [Ordered] ensures that the hashtable is ordered as originally specified. Don't forget -Compress before sending, like others have said.