Howto filter element of map

Terraform
1

Hi all,

I created a map and I need to filter one element of the map. This is my map:

interfaces = {

nic1 = {

name = "main"

ip = "xyz"

primary = true

},

nic2 = {

name = "admin"

ip = "zyx"

primary = false

}

}

I’d like to get only the element where primary = true . I have tried the following:

primary_interface = [

for interface in keys(interfaces):

interfaces[interface]

if interfaces[interface].primary

]

This gives me the following error:

Error: Invalid reference

on main.tf line 12, in locals:

12: interfaces[interface]

A reference to a resource type must be followed by at least one attribute

access, specifying the resource name.

Thanks in advance for any advice you can offer.

2

Hi @suexec92,

If that interfaces declaration is inside a locals block then the correct way to refer to it elsewhere in the configuration is as local.interfaces, not just interfaces.

Currently Terraform thinks you are trying to refer to a resource of type interfaces, because that’s the default handling of any top-level symbol that isn’t considered special by Terraform.

3 
locals {
  interfaces = {
    nic1 = {
      name = "main"
      ip = "xyz"
      primary = true
    },
    nic2 = {
      name = "admin"
      ip = "zyx"
      primary = false
    }
  }
}

output "filter" {
  value = { for k, v in local.interfaces :  k => v if v.primary == true }
}

Something like that?

1 Like
4

Thank you! Prepending “local.” was the key! :slight_smile:

5

Thought about it a bit more and this is probably more what you’re looking for, so you can use the filter to pick from the input array:

bent@DESKTOP-KEO4V17:/tmp/filtermap$ cat main.tf
locals {
  interfaces = {
    nic1 = {
      name = "main"
      ip = "10.0.0.1"
      primary = true
    },
    nic2 = {
      name = "admin"
      ip = "127.0.0.1"
      primary = false
    }
  }

  filter = [ for k, v in local.interfaces :  k if v.primary == true ]
  primary = local.filter[0]
}

output "primary_ip" {
  value = local.interfaces[local.primary].ip
}
bent@DESKTOP-KEO4V17:/tmp/filtermap$ terraform apply

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

primary_ip = 10.0.0.1
bent@DESKTOP-KEO4V17:/tmp/filtermap$
1 Like