PolyEcto

A generic, configurable library for polymorphic associations in Ecto schemas. PolyEcto provides a clean, efficient way to create "belongs to any" and "has many polymorphic" relationships without sacrificing Ecto's familiar patterns.

See the detailed documentation for comprehensive usage examples and API reference.

Features

• Generic & Reusable: Zero hardcoded relationship types - works with any schema
• Ecto-Native API: Feels like standard Ecto associations
• Efficient Queries: Batch loading with no N+1 queries
• Table-Based Storage: Uses stable table names (not module names)
• Type Safe: Full typespecs and compile-time checks
• Zero Dependencies: Pure Ecto, no external libraries

Installation

Add polyecto to your list of dependencies in mix.exs:

def deps do
  [
    {:polyecto, "~> 0.1.0"},
    {:ecto, "~> 3.10"}
  ]
end

Quick Start

1. Create a config module:

defmodule MyApp.PolyEctoConfig do
  @behaviour PolyEcto.Config

  @registry %{
    "posts" => MyApp.Post,
    "comments" => MyApp.Comment
  }

  @reverse_registry Map.new(@registry, fn {k, v} -> {v, k} end)

  @impl true
  def repo, do: MyApp.Repo

  @impl true
  def get_schema(table_name), do: Map.get(@registry, table_name)

  @impl true
  def get_table(schema_module), do: Map.get(@reverse_registry, schema_module)
end

1. Configure it in config/config.exs:

config :polyecto, :config, MyApp.PolyEctoConfig

1. Use in your schemas:

defmodule MyApp.Comment do
  use Ecto.Schema
  import PolyEcto

  schema "comments" do
    polymorphic_belongs_to :commentable
    field :content, :text
    timestamps()
  end

  def changeset(comment, attrs) do
    comment
    |> cast(attrs, [:content])
    |> PolyEcto.cast_polymorphic(:commentable)
  end
end

Documentation

For detailed documentation including:

• Complete usage examples
• Migration patterns
• Best practices
• Performance considerations
• Troubleshooting guide

See the comprehensive README.

License

MIT