How to pass output of two for_each loops in terraform as an input to other tf resource

Terraform
1

I am trying to create a few Azure resources like VNET, Subnet and an NSG. I am making use of for_each meta argument to create multiple subnets and NSG’s. But, I am not able to figure out how to associate them using “azurerm_subnet_network_security_group_association”. I am creating the output of subnet id’s and NSG id’s as a map, but I am not able to figure out how to create a association between subnet ID and NSG ID. For ex: I have a subnet created called “public_subnet” and I want to associate “public_nsg” to public subnet and likewise for private. For now, I just want the assignment to be driven by just the names.

child module main.tf:

resource "azurerm_virtual_network" "vnet" {
  name                = format("%s-%s-vnet", var.owner_custom, var.purpose_custom)
  location            = var.location
  resource_group_name = format("rg-%s-%s", var.owner_custom, var.purpose_custom)
  address_space       = var.address_space

}


resource "azurerm_subnet" "subnet" {
  for_each = var.subnets
  name = each.value["name"]
  address_prefixes = each.value["address_space"]
  resource_group_name = format("rg-%s-%s", var.owner_custom, var.purpose_custom)
  virtual_network_name = azurerm_virtual_network.vnet.name
}


resource "azurerm_network_security_group" "nsg" {
  for_each = var.nsg
  name = each.value["name"]
  location = var.location
  resource_group_name = format("rg-%s-%s", var.owner_custom, var.purpose_custom)
}


resource "azurerm_subnet_network_security_group_association" "nsg_association" {
  subnet_id = #need help here
  network_security_group_id = #need help here
}

child module variables.tf:

variable "owner_custom" {
    description = "Short name of owner"
}

variable "purpose_custom" {
    description = "Custom purpose"
}
variable "location" {
  description = "Location where resource is to be created"
  
}
variable "address_space" {
  type = list
  description = "VNET CIDR Range"
}

variable "subnets" {
  description = "A map to create multiple subnets"
  type = map(object({
    name = string
    address_space = list(string)
  })) 
}

variable "nsg" {
  description = "A map of NSGs"
  type = map(object({
    name = string
  }))
  
}

child module output.tf:

output "vnet_id" {
    value = azurerm_virtual_network.vnet.id
}

output "subnet_id" {
    value = tomap({
        for k, s in azurerm_subnet.subnet : k => s.id
    })
  
}

output "nsg_id" {
    value = tomap({
        for k,s in azurerm_network_security_group.nsg: k => s.id
    })
  
}

tfvars:

#Referenced common across modules
owner_custom = "raghav"
purpose_custom = "demo"

#Referenced in resource-group module
owner = "test@test.com"
purpose = "test"
location = "australiaeast"
org = "org"

#Referenced in network module
address_space = ["10.10.0.0/21"]

subnets = {
    subnet1 = {
        name = "public_subnet"
        address_space = ["10.10.1.0/26"]
        }

    subnet2 = {
        name = "private_subnet"
        address_space = ["10.10.1.64/26"]
        }

    subnet3 = {
        name = "privatelink_subnet"
        address_space = ["10.10.1.128/26"]
        }
    
    subnet4 = {
        name = "AzureFirewallSubnet"
        address_space = ["10.10.1.192/26"]
        }
}

nsg = {
    public_nsg = {
        name = "public_nsg"
        }

    private_nsg = {
        name = "private_nsg"
        }
    }
azure
terraform