Terraform apply - module.instance is a list of object, known after apply

Terraform
1

Hi everyone,
I am stuck in this for a very long time, and I am struggling to find any relevant solution on the internet either.

I have two modules, first creates an EC2 instance, the latter creates ALB, target group and the EC2 instance from the first module is attached to the target group. These are the configurations:

module "instance" {
    source = "../modules/instance"

    count = 1
    
    ami = var.ami
    instance_name = var.instance_name
    instance_type = var.instance_type
    user_data = var.user_data_path
    subnets = ["sg-********"]
    key_name = var.key_name
    monitoring = var.monitoring
    vpc_security_group_ids = [data.aws_security_group.ec2-sg.id]
    
    associate_public_ip_address = var.associate_public_ip_address
}

output "instance_ids" {
    value = one(module.instance[*].instance_ids)
}

module "load-balancer" {

    source = "../modules/load-balancer"

    instance_count = var.alb_count
    load_balancer_type = var.load_balancer_type
    name = var.alb_name
    subnets = var.alb_subnets
    internal = var.is_internal
    security_groups = var.alb_security_groups
    cross_zone_load_balancing = true

    ##application-target-group
    vpc_id = var.vpc_id
    server_type_name = var.server_type_name
    instance_ids = module.instance.instance_ids

    listener = var.listener
    health_check = var.health_check
    target_groups = var.target_groups

    depends_on = [ module.instance ]
}

The root instance module looks something like this:

resource "aws_instance" "this" {
  count = var.instance_count

  ami                    = data.aws_ami.this.id
  instance_type          = var.instance_type
  subnet_id              = var.var.subnets
  key_name               = var.key_name
  vpc_security_group_ids = var.vpc_security_group_ids
  iam_instance_profile   = var.iam_instance_profile
}

And output.tf:

output "instance_ids" {
  description = "The list of instance IDs created."
  value       = aws_instance.this.*.id
}

Any help would be appreciated. Cheers !

Edit: I managed to solve the issue. Had to store the output of the module to locals, and pass the instance the instance id as local argument in load balancer module. The solution looks something like:

locals "instance_ids" {
    value = one(module.instance[*].instance_ids)
}

module "load-balancer" {

    source = "../modules/load-balancer"

    instance_count = var.alb_count
    load_balancer_type = var.load_balancer_type
    name = var.alb_name
    subnets = var.alb_subnets
    internal = var.is_internal
    security_groups = var.alb_security_groups
    cross_zone_load_balancing = true

    ##application-target-group
    vpc_id = var.vpc_id
    server_type_name = var.server_type_name
    instance_ids = local.instance_ids

    listener = var.listener
    health_check = var.health_check
    target_groups = var.target_groups

    depends_on = [ module.instance ]
}