API Query and Negative Value

PowerShell Help
1

I have the following basic code returning a giant array:

$request = 'http://10.111.113.253/api'
$values = Invoke-RestMethod $request
foreach ($value in $values){
    $value.Setpoints.Refrigeration
}

This returns the following values:

RoomTemp : @{current=38.0 F; currentValue=38.0; units=F}
Refrigerant : @{current=R-404A; currentIndex=0; options=System.Object}
MinCompRuntime : @{current=2 MIN; currentValue=2; units=MIN}
MinCompOffTime : @{current=5 MIN; currentValue=5; units=MIN}
AirTempDiff : @{current=1.0 F; currentValue=1.0; units=F}
2ndRoomTemp : @{current=-50.0 F; currentValue=-50.0; units=F}
AuxTemp1 : @{current=T1 Suct Temp; currentIndex=3; options=System.Object}
AuxTemp4 : @{current=T4 Coil Temp; currentIndex=3; options=System.Object}
RefrigFanMode : @{current=Permanent; currentIndex=1; options=System.Object}
FanSpeed : @{current=0.0 %; currentValue=0.0; units=%}
TempUnits : @{current=Fahrenheit; currentIndex=0; options=System.Object}
MultiAirTempControl : @{current=Warmest Air; currentIndex=0; options=System.Object}

I can query/pull the nested values such as:

$value.Setpoints.Refrigeration.AirTempDiff

Which returns:
current currentValue units

1.0 F 1.0 F

However when I try the following I recieve an error:

$value.Setpoints.Refrigeration.2ndRoomTemp

Error:

  • $value.Setpoints.Refrigeration.2ndRoomTemp

  •                                ~

Missing property name after reference operator.
+ CategoryInfo : ParserError: (:slight_smile: , ParentContainsErrorRecordException
+ FullyQualifiedErrorId : MissingPropertyName

I’m assuming this is caused by the one of two things, the “2ndRoomTemp” begins with a number or the negative value it returns, but not 100% sure. I can query all of the values except this one.

Any help or suggestions would be greatly appreciated.

2

It’s probably the 2.

Try $value.Setpoints.Refrigeration.{2ndRoomTemp}

3

Thank you Don! That worked great. Can I ask why this is the case? Is the “-” sign considered a special character in this case? This is discussed here:

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_variables?view=powershell-6&viewFallbackFrom=powershell-Microsoft.PowerShell.Core

C:\PS> ${save-items} = “a”, “b”, “c”
C:\PS> ${save-items}
a
b
c

Is there a better way to handle the possibility of negative values in this case? I’m working with a refrigeration controller API interface so there is a possibility to have other fields with negative values since temperatures can change…

Thank you again!

Kind Regards,

Alan

4

It’s that property names can’t legally start with a digit in .NET (and many languages). The {} is kind of a PowerShell way of working around it anytime you’ve got a normally-illegal name in a variable or property. And yeah, - is not legal in a variable name.

${This! is a stupid “variable” name}

Is actually legal thanks to the {}. Terrible idea, but legal.

5

Another workaround:

PS C:\WINDOWS\system32> $obj = @()
$obj += [pscustomobject]@{
    'MinCompOffTime' = [pscustomobject]@{
        current='5 MIN';
        currentValue='5';
        units='MIN';
    }
}
$obj += [pscustomobject]@{
    'AirTempDiff' = [pscustomobject]@{
        current='1.0 F';
        currentValue='1.0';
        units='F';
    }
}
$obj += [pscustomobject]@{
    '2ndRoomTemp' = [pscustomobject]@{
        current='-50.0 F';
        currentValue='50';
        units='F';
    }
}

PS C:\WINDOWS\system32> $obj.2ndRoomTemp
At line:1 char:6
+ $obj.2ndRoomTemp
+      ~
Missing property name after reference operator.
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : MissingPropertyName
 

PS C:\WINDOWS\system32> $obj.'2ndRoomTemp'

current currentValue units
------- ------------ -----
-50.0 F 50           F