---
name: absinthe-schema
user-invocable: false
description: Use when designing GraphQL schemas with Absinthe. Covers type definitions, interfaces, unions, enums, and schema organization patterns.
---
# Absinthe - Schema Design
Comprehensive guide to designing GraphQL schemas with Absinthe in Elixir.
## Key Concepts
### Type Definitions
```elixir
defmodule MyApp.Schema.Types do
use Absinthe.Schema.Notation
object :user do
field :id, non_null(:id)
field :name, non_null(:string)
field :email, :string
field :posts, list_of(:post) do
resolve &MyApp.Resolvers.User.posts/3
end
field :inserted_at, :datetime
end
object :post do
field :id, non_null(:id)
field :title, non_null(:string)
field :body, :string
field :author, :user do
resolve &MyApp.Resolvers.Post.author/3
end
end
end
```
### Interfaces
```elixir
interface :node do
field :id, non_null(:id)
resolve_type fn
%MyApp.User{}, _ -> :user
%MyApp.Post{}, _ -> :post
_, _ -> nil
end
end
object :user do
interface :node
field :id, non_null(:id)
field :name, non_null(:string)
end
```
### Unions
```elixir
union :search_result do
types [:user, :post, :comment]
resolve_type fn
%MyApp.User{}, _ -> :user
%MyApp.Post{}, _ -> :post
%MyApp.Comment{}, _ -> :comment
_, _ -> nil
end
end
```
### Enums
```elixir
enum :post_status do
value :draft, as: "draft"
value :published, as: "published"
value :archived, as: "archived"
end
```
### Input Objects
```elixir
input_object :create_post_input do
field :title, non_null(:string)
field :body, :string
field :status, :post_status, default_value: :draft
end
```
## Best Practices
1. **Organize types by domain** - Group related types in separate modules
2. **Use non_null sparingly** - Only for truly required fields
3. **Leverage interfaces** - For shared fields across types
4. **Define input objects** - For complex mutation arguments
5. **Use custom scalars** - For dates, UUIDs, JSON, etc.
## Schema Organization
```elixir
defmodule MyApp.Schema do
use Absinthe.Schema
import_types MyApp.Schema.Types
import_types MyApp.Schema.Queries
import_types MyApp.Schema.Mutations
import_types MyApp.Schema.Subscriptions
import_types Absinthe.Type.Custom # DateTime, etc.
query do
import_fields :user_queries
import_fields :post_queries
end
mutation do
import_fields :user_mutations
import_fields :post_mutations
end
subscription do
import_fields :post_subscriptions
end
end
```
## Custom Scalars
```elixir
scalar :uuid, name: "UUID" do
serialize &to_string/1
parse &parse_uuid/1
end
defp parse_uuid(%Absinthe.Blueprint.Input.String{value: value}) do
case Ecto.UUID.cast(value) do
{:ok, uuid} -> {:ok, uuid}
:error -> :error
end
end
defp parse_uuid(_), do: :error
```
## Anti-Patterns
- Avoid deeply nested types without pagination
- Don't expose database IDs directly without consideration
- Avoid circular dependencies in type definitions
- Don't skip field descriptions for documentation