Assigning multiple public subnet to route table using for each - amazon-web-services

Question

I have multiple subnets created with for each that I am trying to get associated with a route table. Below is the code I have, error, and what I have tried.
locals {
az_names = data.aws_availability_zones.azs.names
pub_sub_ids = aws_subnet.public.*.id
}
resource "aws_route_table_association" "main" {
for_each = var.public_sub_cidr
subnet_id = local.pub_sub_ids[each.key]
route_table_id = aws_route_table.main.id
}
resource "aws_subnet" "public" {
for_each = { for index, az_name in local.az_names : index => az_name }
vpc_id = aws_vpc.main.id
cidr_block = cidrsubnet(var.vpc_cidr, 8, each.key + 1)
availability_zone = local.az_names[each.key]
map_public_ip_on_launch = true
tags = {
Name = "${var.vpc_tags}-PubSubnet"
}
}
Error: Unsupported attribute
on vpc.tf line 3, in locals:
3: pub_sub_ids = aws_subnet.public.*.id
This object does not have an attribute named "id".
I believe this should be working. Any advice on this error and getting these public subnets to attach to the route table would be helpful.
UPDATE
I made some changes and removed the local variable 'pub_sub_ids' and also changed 'aws_route_table_association" "main" to
resource "aws_route_table_association" "main" {
for_each = var.public_sub_cidr
subnet_id = each.key
route_table_id = aws_route_table.main.id
}
Now I am getting an error
Error: Error creating route table association: InvalidSubnetID.NotFound: The `subnet ID '' does not exist`
It says the subnet does not exist even though I see it in the Console. Any advice would be appreciated in associating these public subnets to the route table.

Answer 1

subnet_id in aws_route_table_association should be subnet id, not subnet CIDR.
Since aws_route_table is not given, I made my own to verify the setup. Thus you could do the following:
resource "aws_route_table_association" "main" {
count = length(aws_subnet.public)
subnet_id = aws_subnet.public[count.index].id
route_table_id = aws_route_table.main.id
}
And below is the full code I used for verification:
provider "aws" {
# your data
}
data "aws_availability_zones" "azs" {
state = "available"
}
locals {
az_names = data.aws_availability_zones.azs.names
}
variable "vpc_cidr" {
default = "10.0.0.0/16"
}
resource "aws_vpc" "main" {
cidr_block = var.vpc_cidr
}
resource "aws_subnet" "public" {
for_each = {for index, az_name in local.az_names: index => az_name}
vpc_id = aws_vpc.main.id
cidr_block = cidrsubnet(var.vpc_cidr, 8, each.key + 1)
availability_zone = local.az_names[each.key]
map_public_ip_on_launch = true
}
resource "aws_internet_gateway" "gw" {
vpc_id = aws_vpc.main.id
tags = {
Name = "main"
}
}
resource "aws_route_table" "main" {
vpc_id = aws_vpc.main.id
route {
cidr_block = "0.0.0.0/0"
gateway_id = aws_internet_gateway.gw.id
}
}
resource "aws_route_table_association" "main" {
count = length(aws_subnet.public)
subnet_id = aws_subnet.public[count.index].id
route_table_id = aws_route_table.main.id
}