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Absinthe cheat sheet

Absinthe cheat sheet. Explore our ultimate quick reference for Absinthe.

This Absinthe Cheat Sheet offers a concise overview of essential concepts and components for building GraphQL APIs in Elixir. It covers the fundamental building blocks such as Schema, Resolver, and Type, demonstrating how they interact within the Phoenix framework to define and resolve GraphQL queries. The cheat sheet includes code snippets for router configuration, schema definition, resolver functions, and type specification, making it a practical guide for developers working with Absinthe and GraphQL in Elixir projects.

Introduction

Concepts

  • Schema - The root. Defines what queries you can do, and what types they return.
  • Resolver - Functions that return data.
  • Type - A type definition describing the shape of the data you'll return.

Plug

web/router.ex

defmodule Blog.Web.Router do
  use Phoenix.Router

  forward "/", Absinthe.Plug,
    schema: Blog.Schema
end

Absinthe is a Plug, and you pass it one Schema.

Main concepts

Schema

web/schema.ex

defmodule Blog.Schema do
  use Absinthe.Schema
  import_types Blog.Schema.Types

  query do
    @desc "Get a list of blog posts"
    field :posts, list_of(:post) do
      resolve &Blog.PostResolver.all/2
    end
  end
end

This schema will account for { posts { ··· } }. It returns a Type of :post, and delegates to a Resolver.

Resolver

web/resolvers/post_resolver.ex

defmodule Blog.PostResolver do
  def all(_args, _info) do
    {:ok, Blog.Repo.all(Blog.Post)}
  end
end

This is the function that the schema delegated the posts query to.

Type

web/schema/types.ex

defmodule Blog.Schema.Types do
  use Absinthe.Schema.Notation

  @desc "A blog post"
  object :post do
    field :id, :id
    field :title, :string
    field :body, :string
  end
end

This defines a type :post, which is used by the resolver.

Schema

Query arguments

GraphQL query

{ user(id: "1") { ··· } }

web/schema.ex

query do
  field :user, type: :user do
    arg :id, non_null(:id)
    resolve &Blog.UserResolver.find/2
  end
end

{: data-line="3"}

Resolver

def find(%{id: id} = args, _info) do
  ···
end

Mutations

GraphQL query

{
  mutation CreatePost {
    post(title: "Hello") { id }
  }
}

web/schema.ex

mutation do
  @desc "Create a post"
  field :post, type: :post do
    arg :title, non_null(:string)
    resolve &Blog.PostResolver.create/2
  end
end

References

LISTEN