🐥 Sorting with custom order in Elixir

In our previous post, we sorted JavaScript objects by a custom order using a rank map. Elixir can do the same—just as cleanly.

Let’s say you have a list of maps representing issues:

tickets = [
  %{type: :medium,  title: "Scrollbar jitter"},
  %{type: :critical, title: "Data loss on save"},
  %{type: :low,     title: "Typo in footer"},
  %{type: :high,    title: "Broken login link"}
]

And you want them sorted as: :critical → :high → :medium → :low.

First, we define a rank map

severity_rank = %{
  critical: 0,
  high: 1,
  medium: 2,
  low: 3
}

This can then be used to sort using Enum.sort_by:

Enum.sort_by(tickets, fn ticket ->
  Map.get(severity_rank, ticket.type, :infinity)
end)

Unknown types (e.g., typos or missing values) will land at the end thanks to :infinity.

If you'd rather fail fast on unknown types:

Enum.sort_by(tickets, fn ticket ->
  Map.fetch!(severity_rank, ticket.type)
end)

If you use the same order across modules:

@severity_rank %{critical: 0, high: 1, medium: 2, low: 3}

Then:

Enum.sort_by(tickets, &Map.fetch!(@severity_rank, &1.type))