How to get an object from a list of objects in Terraform?

Question

I have the following list of objects variable:

variable "objects" {   type = "list"   description = "list of objects   default = [       {         id = "name1"         attribute = "a"       },       {         id = "name2"         attribute = "a,b"       },       {         id = "name3"         attribute = "d"       }   ] } 

How do I get element with id = "name2" ?

Answer 1

You get the map with id="name2" with the following expression:

var.objects[index(var.objects.*.id, "name2")] 

For a quick test, run the following one-liner in terraform console:

[{id = "name1", attribute = "a"}, {id = "name2", attribute = "a,b"}, {id = "name3", attribute = "d"}][index([{id = "name1", attribute = "a"}, {id = "name2", attribute = "a,b"}, {id = "name3", attribute = "d"}].*.id, "name2")] 

Answer 2

You can't nested multiple levels of square brackets to get n levels inside a data structure. However you can use the interpolation functions to retrieve such values. In this case you'll want to use the lookup function to retrieve the value from the map which itself has been accessed with square brackets, that will look like this...

${lookup(var.objects[1], "id")} 

Rowan is correct, complex data structures are difficult to work with in current versions of Terraform. However it looks like it won't be too long before we can expect better support in this area. The upcoming version 0.12 will include rich types adding improvements to lists and maps.