How to reference a parameter within a parameter in an ARM template? - azure

Question

I can't seem to find any way to use the value of a parameter as part of another parameter in a parameter file for ARM templates:
{
"$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"someCustomParam": {
"value": "desired value"
},
"tags": {
"value": {
"tag1": "[parameters('someCustomParam')]",
"tag2": "some tag value"
}
},
}
}
Notice how I want to use the value of a previous parameter for the value of another.
The value for "tag1" is simply the string and the value does not get substituted in from the parameter() function. I've tested this by using the Test-AzResourceGroupDeployment PowerShell cmdlet.
Is there any way I can do this?

Answer 1

You can do this using PowerShell. Before calling Test-AzResourceGroupDeployment you can get content of parameter file in PowerShell variable/object using
$ParameterObject = Get-Content ./ParameterFileName.json
Update required value like:
$ParameterObject.parameters.tags.value.tag1 = #Value to assign
Pass $parameterObject to -TemplateParameterObject parameter of Test-AzResourceGroupDeployment
------OR------
Convert $parameterObject to JSON using ConvertTo-Json and Save as temp.json and pass temp.json to -TemplateParameterFile [reference below]
$TempParameterFile = ( $ParametersObject | ConvertTo-Json -Depth 20 ) -replace "\\u0027", "'" -replace "\\u0026", "&" | Out-File $tmp -Force
and use $TempParameterFile for -TemplateParameterFile

Answer 2

You need to use variables.
In variables, you can use "[parameters('parameterName')]".
And you can use variables in a similar way as parameters : "[variables('variableName')]"
Update:
Here is a sample:
"parameters": {
"someCustomParam": {
"type": "string"
}
},
"variables": {
"tags": {
"tag1": "[parameters('someCustomParam')]",
"tag2": "some tag value"
}
}
And then you can use the variable in the resource of your template.

Answer 3

You can do this just like what you normally do when you reference a parameter, an example as following:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentParameters.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"paramOne": {
"value": "hello"
},
"paramTwo": {
"value": "[concat(parameters('paramOne'), '-', 'world)]"
}
}
}
the output value of 'paramTwo' will be 'hello-world'.
Hope this helps whoever wants to utilize referencing a parameter in a parameter in a parameter file.