Elixir - How to convert keyword list to string?

Question

I have a keyword list: [key1: "value", key2: "value2", key3: "value3"]

I want to convert it into a string: "key1:value1&key2:value2&key3:value3"

I was thinking to use Enum.reduce, but what will be the arguments to the function?

Answer 1

Since you want to add a separator between the values after mapping them, I'd suggest using Enum.map_join/3:

iex(1)> list = [key1: "value", key2: "value2", key3: "value3"]
[key1: "value", key2: "value2", key3: "value3"]
iex(2)> list |> Enum.map_join("&", fn {k, v} -> "#{k}:#{v}" end)
"key1:value&key2:value2&key3:value3"

This is how you can do it with Enum.reduce/3 (There's an extra & inserted at the start which is being removed using String.trim_leading/1):

iex(3)> list |> Enum.reduce("", fn {k, v}, acc -> "#{acc}&#{k}:#{v}" end) |> String.trim_leading("&")
"key1:value&key2:value2&key3:value3"