keys

Array[P] keys(Map[P, Y])
Array[String] keys(Struct|Object)

Given a key-value type collection (Map, Struct, or Object), returns an Array of the keys from the input collection, in the same order as the elements in the collection.

When the argument is a Struct, the returned array will contain the keys in the same order they appear in the struct definition. When the argument is an Object, the returned array has no guaranteed order.

When the input Map or Object is empty, an empty array is returned.

Parameters

1. Map[P, Y]|Struct|Object: Collection from which to extract keys.

Returns: Array[P] of the input collection's keys. If the input is a Struct or Object, then the returned array will be of type Array[String].

Example: test_keys.wdl

version 1.2

struct Name {
  String first
  String last
}

workflow test_keys {
  input {
    Map[String, Int] x = {"a": 1, "b": 2, "c": 3}
    Map[String, Pair[File, File]] str_to_files = {
      "a": ("data/questions.txt", "data/answers.txt"),
      "b": ("data/request.txt", "data/response.txt")
    }
    Name name = Name {
      first: "John",
      last: "Doe"
    }
  }

  scatter (item in as_pairs(str_to_files)) {
    String key = item.left
  }

  Array[String] str_to_files_keys = key
  Array[String] expected = ["a", "b", "c"]
  Array[String] expectedKeys = ["first", "last"]

  output {
    Boolean is_true1 = length(keys(x)) == 3 && keys(x) == expected
    Boolean is_true2 = str_to_files_keys == keys(str_to_files)
    Boolean is_true3 = length(keys(name)) == 2 && keys(name) == expectedKeys
  }
}

{}

{
  "test_keys.is_true1": true,
  "test_keys.is_true2": true,
  "test_keys.is_true3": true
}