How do I access an attribute from a counted resource within another resource?

Question

I'm using Terraform to script an AWS build. I'm spinning up a number of instances across multiple availability zones, in this example, 2:

resource "aws_instance" "myinstance" {
    count                   = 2
    ami                     = "${var.myamiid}"
    instance_type           = "${var.instancetype}"
    availability_zone       = "${data.aws_availability_zones.all.names[count.index]}"
    # other details omitted for brevity
}

I now need to assign an Elastic IP to these instances, so that I can rebuild the instances in the future without their IP address changing. The below shows what I'd like to do:

resource "aws_eip" "elastic_ips" {
    count    = 2
    instance = "${aws_instance.myinstance[count.index].id}"
    vpc      = true
}

But this errors with:

expected "}" but found "."

I've also tried using lookup:

instance = "${lookup(aws_instance.sbc, count.index).id}"

but that fails with the same error.

How can I go about attaching Elastic IPs to these instances?

Answer 1

This works for me,

instance = aws_instance.myinstance.*.id