Terraform - Specifying multiple possible values for Variables

问题

CloudFormation provides AllowedValues for Parameters which tells that the possible value of the parameter can be from this list. How can I achieve this with Terraform variables? The variable type of list does not provide this functionality. So, in case I want my variable to have value out of only two possible values, how can I achieve this with Terraform. CloudFormation script that I want to replicate is:

"ParameterName": {
        "Description": "desc",
        "Type": "String",
        "Default": true,
        "AllowedValues": [
            "true",
            "false"
        ]
   }

回答1:

I don't know of an official way, but there's an interesting technique described in a Terraform issue:

variable "values_list" {
  description = "acceptable values"
  type = "list"
  default = ["true", "false"]
}

variable "somevar" {
description = "must be true or false"
}

resource "null_resource" "is_variable_value_valid" {
  count = "${contains(var.values_list, var.somevar) == true ? 0 : 1}"
  "ERROR: The somevar value can only be: true or false" = true
}

来源：https://stackoverflow.com/questions/54254524/terraform-specifying-multiple-possible-values-for-variables