How Novistore is using GraphQL in Elixir to build a next-generation e-commerce platform.

1. GraphQL meets Elixir
An introduction to GraphQL
and how to use it in Elixir and Vue.js

2. Jeroen Visser
CTO at Novistore

3. Novistore
e-commerce SaaS
novi.store

4. What is GraphQL?

5. What is GraphQL?
A way to talk to your app
as if it were a database.

6. Graph

7. Graph
Shop
Products
Reviews

8. Graph
Shop
Products
Reviews
query {
name
title
description
price
title
body
}
}
}
}
products {
shop {
reviews {

9. Query and Mutation

10. Mutation
query productsByShopId($id: ID!) {
shop(id: $id) {
name
products {
title
description
price
reviews {
title
body
}
}
}
}
// Variables
{ "id": 3236 }
Query
mutation createProduct(
$input: ProductInputObject!
) {
product: createProduct(
input: $input
) {
title
description
price
}
}
// Variables
{
"input": {
"title": "Apple iPhone X — 64GB",
"price": 104999,
"description": "Our vision has always
been to create an iPhone ..."
}
}

11. Absinthe
{:absinthe, "~> 1.4"}

12. Schema
defmodule Novistore.Schema do
use Absinthe.Schema
import_types Novistore.Type.Review
import_types Novistore.Type.Product
query do
import_fields :review_queries
import_fields :product_queries
end
mutation do
import_fields :product_mutations
import_fields :review_mutations
end
end

13. Type
defmodule Novistore.Type.Product do
use Absinthe.Schema.Notation
use Absinthe.Ecto, repo: Novistore.Repo
# ...
input_object :product_input_object do
# ...
end
object :product_queries do
# ...
end
# ... mutations, resolvers
end
object :product_object do
end

14. Object
field :id, :id
field :title, :string
field :description, :string
field :price, :integer
field :reviews,
list_of(:review_object),
resolve: assoc(:reviews)
object :product_object do
end

15. Input Object
input_object :product_input_object do
field :title, :string
field :description, :string
field :price, :integer
end

16. Query
object :product_queries do
field :product_by_id, :product_object do
arg :id, non_null(:id)
resolve &product_by_id/2
end
end

17. Mutation
object :product_mutations do
field :create_product, :product_object do
arg :input, non_null(:product_input_object)
resolve &create_product/2
end
end

18. Resolver
defp product_by_id(%{id: id}, _context) do
Novistore.product_by_id(id)
end
defp create_product(%{input: input}, _context) do
Novistore.create_product(input)
end

19. Authorization

20. Authorization: Bearer <token>

21. Step 1: Plug
defp parse_token(conn) do
case get_req_header(conn, "authorization") do
["Bearer " <> token] -> {:ok, token}
_ -> {:error, :not_found}
end
end

22. Step 2: Middleware
def call(%{context: %{token: token}} = resolution, _) do
with {:ok, session} <- Novistore.session_by_token(token),
{:ok, context} <- create_context(session) do
%{resolution | context: context}
end
end

23. Step 2: Middleware
defmodule Novistore.AuthMiddleware do
@behaviour Absinthe.Middleware
def call(%{context: %{
user: %User{status: "active"}
}} = resolution, _config) do
resolution
end
def call(resolution, _config) do
Absinthe.Resolution.put_result(
resolution, {:error, :unauthenticated}
)
end
end

24. Step 2: Middleware
object :product_mutations do
field :create_product, :product_object do
arg :input, non_null(:product_input_object)
middleware AuthMiddleware
resolve &create_product/2
middleware ErrorMiddleware
end
end

25. Step 3: Resolver Permissions
defp product_by_id(%{id: id}, %{context: context}) do
with :ok <- may?(context, read(:product)),
{:ok, product} <- wrap(&Novistore.product_by_id/1, id),
:ok <- can?(context, read(product)) do
{:ok, product}
end
end

26. Demo time