Map helper functions: keys(), values()

[gtrevg]

Is there an easy way to get only the keys or values defined in a map? For example, given:

variable "aws_az_subnet_map" {
  description = "The subnet id for each availability zone"
  default = {
    us-west-2a = "subnet-abcd1234"
    us-west-2b = "subnet-efab5678"
    us-west-2c = "subnet-cdef9012"
  }
}

It would allow you to easily just dump either the keys or values into other parts of the configuration.

resource "aws_elb" "my_elb" {
    subnets = [ "${values(var.aws_az_subnet_map)}" ]
}

resource "aws_autoscaling_group" "my_autoscale_group" {
    availability_zones = [ "${keys(var.aws_az_subnet_map)}" ]
    vpc_zone_identifier = [ "${values(var.aws_az_subnet_map)}" ]
}

resource "aws_instance" "my_instance" {
    count = "${length( keys(var.aws_az_subnet_map))}"
    subnet_id = "${ element(values(var.aws_az_subnet_map)), count.index }"
}

This keeps one form having to maintain two variables that then must remain in sync with the correct number of items in each.

Thanks

[radeksimko]

That's actually an interesting idea. There isn't AFAIK a such built-in function yet.

[mikeyhill]

+1 this would be much more graceful than hardcoding those individual values in

[phinze]

Yep I think this would be a great idea. A PR would be welcome, or one of us core folk will try to pick it up when we can.

Worth noting that the functionality would be limited to direct variable access w/ defaults until we enhance the config language to fully support complex types. Still worth adding IMO.

[edmundcraske]

Doesn't seem like these functions are documented in the main Terraform docs yet?

[radeksimko]

@edmundcraske See 8036528 It was documented about a month ago, docs website will be updated along with the next release. 😉

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