ARM Template Copy function not picking values form parameter - azure

Question

Hi I have created a simple ARM template to create Route table and routes, I am trying to use Copy function in properties to define routes based on the Parameter Array. following is the code written
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"routetablename": {
"type": "string",
"defaultValue": "DDS-SHD-ROUTETABLE",
"metadata": {
"displayName": "Route Table Name"
}
},
"disableBgpRoutePropagation": {
"type": "string",
"defaultValue": "false",
"metadata": {
"description": "Route Propagation."
}
},
"DD": {
"type": "array",
"defaultValue": [
"10.0.0.0/24",
"10.1.0.0/24",
"10.2.0.0/24"],
"metadata": {
"description": "OnPremises Address Prefix for Subnet01."
}
},
"tagvalue": {
"type": "string",
"defaultValue": "Shared Network Services",
"metadata": {
"description": "Tag Value for Resource."
}
},
"location": {
"type": "string",
"defaultValue": "[resourceGroup().location]",
"metadata": {
"description": "Location for all resources."
}
}
},
"variables": {
"routetablename": "[parameters('routetablename')]",
"tagvalue": "[parameters('tagvalue')]",
"location": "[parameters('location')]"
},
"resources": [
{
"name": "[variables('routetablename')]",
"type": "Microsoft.Network/routeTables",
"apiVersion": "2019-02-01",
"location": "[variables('location')]",
"tags": {
"app": "[variables('tagvalue')]"
},
"dependsOn": [],
"properties": {
"disableBgpRoutePropagation": "[parameters('disableBgpRoutePropagation')]",
"Copy":
[
{
"name": "routes",
"count": "[length(parameters('DD'))]",
"input": {
"name": "[concat('OnPrem',copyIndex('routes'))]",
"addressPrefix": "[parameters('DD')]",
"nextHopType": "VirtualNetworkGateway"
}
}
]
}
}
]
}
As per My understanding the I sshould get 1 Route table with 3 routes namely
Onprem0
OnPrem1
OnPrem2
Instead I get following error:
"details": [
{
"code": "AddressPrefixStringCannotBeNullOrEmpty",
"message": "Address prefix string for resource /subscriptions/.../resourceGroups/CAZAUSE-MGMT-NETWORK-RG/providers/Microsoft.Network/routeTables/DDS-SHD-ROUTETABLE/routes/OnPrem0 cannot be null or empty.",
"details": []
Any help will be appreciated.

Answer 1

Got this Fixed was missing the COpyIndex() in AddressSuffix Parameter as follows
"Copy":
[
{
"name": "routes",
"count": "[length(parameters('DD'))]",
"input": {
"name": "[concat('OnPrem-',copyIndex('routes'))]",
"properties": {
"addressPrefix": "[parameters('DD')[copyIndex('routes')]]",
"nextHopType": "VirtualNetworkGateway"