DifferEcto

Ecto.Type for Differ (and some helpers)

Installation

The package can be installed by adding differ_ecto to your list of dependencies in mix.exs:

def deps do
  [
    {:differ_ecto, "~> 0.1-pre"}
  ]
end

Documentation

Documentation can be found at https://hexdocs.pm/differ_ecto.

Usage

You can use json array to store diffs like this

defmodule Example do
  use Ecto.Schema
  # gives us Diffable, Patchable and Diff
  use DifferEcto

  # we have to skip :diffs field
  # skip timestamps as well
  @derive [{Diffable, skip: [:updated_at, :diffs]}, Patchable]
  schema "example" do
    field :body, :string
    field :title, :string
    # we want to store list of diffs in document
    field :diffs, {:array, Diff}, default: []
    timestamps()
  end
end

then when you do updates, you need to calculate diffs

  def update(%Example{} = ex, attrs) do
    import Ecto.Changeset
    ex
    |> Example.changeset(attrs)
    |> Repo.update()
    |> case do
      # after successful update run diff
      {:ok, new_ex} ->
        diff = DifferEcto.diff(ex, new_ex)
        new_diffs = [diff | List.wrap(ex.diffs)]

        # save diff to list of diffs
        new_ex 
        |> cast(%{diffs: new_diffs}, [:diffs])
        |> Repo.update()
      val ->
        val
    end