# Freight
Freight is a library for [Absinthe GraphQL](http://absinthe-graphql.org/) that helps you build mutation payload results. Inspired by the GraphQL APIs of [GitHub](https://developer.github.com/v4/breaking_changes/) and [Shopify](https://gist.github.com/swalkinshaw/3a33e2d292b60e68fcebe12b62bbb3e2), who also aim to keep syntactical GraphQL errors, like missing fields and malformed queries, seperate from validation and other business logic errors.
It is heavily inspired by [Kronky](https://github.com/Ethelo/kronky), I decided to build my own library because I did not like how much it is focussed on ecto changesets, and missed customisability that was required for a project I work on.
## Configuration
You can set a custom error object that will be returned in the errors array in your payloads. This object must be defined in the schema you're calling `define_payload` from.
```elixir
config :freight,
error_object: :user_error
# whenever a field is snake-cased (like an ecto field for example), setting this to `true` will camelize it like Absinthe would
lower_camelize_field_name: true
```
## Usage
Below is a documented example of how to define Freight payloads in your schema
```elixir
defmodule FreightDemo.Schema.Example do
use Absinthe.Schema.Notation
import Freight.Payload
object :user do
field(:name, :string)
end
object :comment do
field(:body, :string)
field(:author, :user)
end
define_payload(:create_comment_payload, author: :user, comment: :comment)
field :create_comment, type: :create_comment_payload do
arg(:body, non_null(:string))
resolve(&FreightDemo.Resolver.create_comment/3)
middleware(&build_payload/2)
end
end
```
Returning errors works just like in Absinthe
```elixir
defmodule FreightDemo.Resolver do
def create_comment(_parent, %{body: body}, _context) do
# your logic
{:ok, author: %{}, comment: %{}}
end
# OR
def create_comment(_parent, %{body: body}, _context) do
# your logic
{:error, "Something went horribly wrong!"}
end
end
```
More extensive documentation on defining errors can be found in the [documentation](https://hexdocs.pm/freight)
## Installation
Add the following to your `mix.exs file`
```elixir
def deps do
[
{:freight, "~> 0.4.0"}
]
end
```
Documentation can be found at [https://hexdocs.pm/freight](https://hexdocs.pm/freight).
