Absinthe Helpers
This package provides two key features:
- constraints: enforce validation rules (like
min
,max
, etc.) on fields and arguments in your schema. - transforms: apply custom transformations (like
Trim
,ToInteger
, etc.) to input fields and arguments.
Installation
Add absinthe_helpers
to your list of dependencies in mix.exs
:
def deps do
[
{:absinthe_helpers, "~> 0.1.0"}
]
end
Then, run:
mix deps.get
Setup: adding constraints and transforms to your Absinthe pipeline
To set up both constraints and transforms, follow these steps:
- Add constraints and transforms to your Absinthe pipeline:
forward "/graphql",
to: Absinthe.Plug,
init_opts: [
schema: MyProject.Schema,
pipeline: {__MODULE__, :absinthe_pipeline},
]
def absinthe_pipeline(config, opts) do
config
|> Absinthe.Plug.default_pipeline(opts)
|> AbsintheHelpers.Phases.ApplyConstraints.add_to_pipeline(opts)
|> AbsintheHelpers.Phases.ApplyTransforms.add_to_pipeline(opts)
end
- Add constraints to your schema:
defmodule MyApp.Schema do
use Absinthe.Schema
@prototype_schema AbsintheHelpers.Directives.Constraints
# ...
end
Constraints
The constraints
directive allows you to enforce validation rules on fields and arguments in your GraphQL schema. Constraints are applied at the schema level and are visible in the GraphQL schema, making them accessible to the frontend.
Example: graphql schema with constraints
"Overrides for location-specific service pricing."
input LocationOverrideInput {
duration: Int @constraints(min: 300, max: 43200)
price: Decimal @constraints(min: 0, max: 100000000)
priceType: ServicePriceType
locationId: ID!
}
How to use constraints
- Apply constraints to a field or argument:
field :my_list, list_of(:integer) do
directive(:constraints, [min_items: 2, max_items: 5, min: 1, max: 100])
resolve(&MyResolver.resolve/3)
end
field :my_field, :integer do
arg :my_arg, non_null(:string), directives: [constraints: [min: 10]]
resolve(&MyResolver.resolve/3)
end
Transforms
Transforms allow you to modify or coerce input values at runtime. You can apply these transformations to individual fields, lists, or arguments in your Absinthe schema.
Example: applying transforms in your schema
- Apply transforms directly to a field:
alias AbsintheHelpers.Transforms.ToInteger
alias AbsintheHelpers.Transforms.Trim
alias AbsintheHelpers.Transforms.Increment
field :employee_id, :id do
meta transforms: [Trim, ToInteger, {Increment, 3}]
end
- Apply transforms to a list of values:
field :employee_ids, non_null(list_of(non_null(:id))) do
meta transforms: [Trim, ToInteger, {Increment, 3}]
end
- Apply transforms to an argument:
field(:create_booking, :string) do
arg(:employee_id, non_null(:id),
__private__: [meta: [transforms: [Trim, ToInteger, {Increment, 3}]]]
)
resolve(&TestResolver.run/3)
end