absinthe_federation's Introduction

Absinthe.Federation

Installation

Install from Hex.pm:

def deps do
  [
    {:absinthe_federation, "~> 0.1.9"}
  ]
end

Install from github:

def deps do
  [
    {:absinthe_federation, github: "DivvyPayHQ/absinthe_federation", branch: "main"}
  ]
end

Add the following line to your absinthe schema

defmodule MyApp.MySchema do
  use Absinthe.Schema
+ use Absinthe.Federation.Schema

  query do
    ...
  end
end

Usage

Macro based schemas (recommended)

defmodule MyApp.MySchema do
  use Absinthe.Schema
+ use Absinthe.Federation.Schema

  query do
+   extends()

    field :review, :review do
      arg(:id, non_null(:id))
      resolve(&ReviewResolver.get_review_by_id/3)
    end
    ...
  end

  object :product do
+   key_fields("upc")
+   extends()

    field :upc, non_null(:string) do
+     external()
    end

    field(:reviews, list_of(:review)) do
      resolve(&ReviewResolver.get_reviews_for_product/3)
    end

+   field(:_resolve_reference, :product) do
+     resolve(&ProductResolver.get_product_by_upc/3)
+   end
  end
end

SDL based schemas (experimental)

defmodule MyApp.MySchema do
  use Absinthe.Schema
+ use Absinthe.Federation.Schema

  import_sdl """
    extend type Query {
      review(id: ID!): Review
    }

    extend type Product @key(fields: "upc") {
      upc: String! @external
      reviews: [Review]
    }
  """

  def hydrate(_, _) do
    ...
  end

Resolving structs in _entities queries

If you need to resolve your struct to a specific type in your schema you can implement the Absinthe.Federation.Schema.EntityUnion.Resolver protocol like this:

defmodule MySchema do
  @type t :: %__MODULE__{
          id: String.t()
        }

  defstruct id: ""

  defimpl Absinthe.Federation.Schema.EntityUnion.Resolver do
    def resolve_type(_, _), do: :my_schema_object_name
  end
end