159 lines
2.6 KiB
Markdown
159 lines
2.6 KiB
Markdown
---
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title: Absinthe
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category: Hidden
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tags: [WIP]
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updated: 2017-10-10
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intro: |
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[Absinthe](http://absinthe-graphql.org/) allows you to write GraphQL servers in Elixir.
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---
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## Introduction
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### Concepts
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- `Schema` - The root. Defines what queries you can do, and what types they return.
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- `Resolver` - Functions that return data.
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- `Type` - A type definition describing the shape of the data you'll return.
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### Plug
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#### web/router.ex
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```elixir
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defmodule Blog.Web.Router do
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use Phoenix.Router
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forward "/", Absinthe.Plug,
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schema: Blog.Schema
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end
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```
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{: data-line="4,5"}
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Absinthe is a Plug, and you pass it one **Schema**.
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See: [Our first query](http://absinthe-graphql.org/tutorial/our-first-query/)
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## Main concepts
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{: .-three-column}
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### Schema
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#### web/schema.ex
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```elixir
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defmodule Blog.Schema do
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use Absinthe.Schema
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import_types Blog.Schema.Types
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query do
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@desc "Get a list of blog posts"
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field :posts, list_of(:post) do
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resolve &Blog.PostResolver.all/2
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end
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end
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end
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```
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{: data-line="5,6,7,8,9,10"}
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This schema will account for `{ posts { ··· } }`. It returns a **Type** of `:post`, and delegates to a **Resolver**.
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### Resolver
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#### web/resolvers/post_resolver.ex
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```elixir
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defmodule Blog.PostResolver do
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def all(_args, _info) do
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{:ok, Blog.Repo.all(Blog.Post)}
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end
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end
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```
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{: data-line="3"}
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This is the function that the schema delegated the `posts` query to.
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### Type
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#### web/schema/types.ex
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```elixir
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defmodule Blog.Schema.Types do
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use Absinthe.Schema.Notation
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@desc "A blog post"
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object :post do
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field :id, :id
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field :title, :string
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field :body, :string
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end
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end
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```
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{: data-line="4,5,6,7,8,9"}
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This defines a type `:post`, which is used by the resolver.
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## Schema
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### Query arguments
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#### GraphQL query
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```
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{ user(id: "1") { ··· } }
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```
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#### web/schema.ex
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```elixir
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query do
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field :user, type: :user do
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arg :id, non_null(:id)
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resolve &Blog.UserResolver.find/2
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end
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end
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```
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{: data-line="3"}
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#### Resolver
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```elixir
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def find(%{id: id} = args, _info) do
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···
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end
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```
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{: data-line="1"}
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See: [Query arguments](http://absinthe-graphql.org/tutorial/query-arguments/)
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### Mutations
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#### GraphQL query
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```
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{
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mutation CreatePost {
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post(title: "Hello") { id }
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}
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}
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```
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#### web/schema.ex
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```elixir
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mutation do
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@desc "Create a post"
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field :post, type: :post do
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arg :title, non_null(:string)
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resolve &Blog.PostResolver.create/2
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end
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end
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```
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{: data-line="1"}
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See: [Mutations](http://absinthe-graphql.org/tutorial/mutations/)
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## References
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- [Absinthe website](http://absinthe-graphql.org/) _(absinthe-graphql.org)_
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- [GraphQL cheatsheet](./graphql) _(devhints.io)_
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