Input Objects

Defining Input Object Types
Using Input Objects
Customizing Input Objects
Converting to Other Ruby Objects
@oneOf

Input object types are complex inputs for GraphQL operations. They’re great for fields that need a lot of structured input, like mutations or search fields. In a GraphQL request, it might look like this:

mutation {
  createPost(attributes: { title: "Hello World", fullText: "This is my first post", categories: [GENERAL] }) {
    #                    ^ Here is the input object ..................................................... ^
  }
}

Like a Ruby Hash, an input object consists of keys and values. Unlike a Hash, its keys and value types must be defined statically, as part of the GraphQL system. For example, here’s an input object, expressed in the GraphQL Schema Definition Language (SDL):

input PostAttributes {
  title: String!
  fullText: String!
  categories: [PostCategory!]
}

This input object has three possible keys:

title is required (denoted by !), and must be a String
fullText is also a required String
categories is optional (it doesn’t have !), and if present, it must be a list of PostCategory values.

Defining Input Object Types

Input object types extend GraphQL::Schema::InputObject and define key-value pairs with the argument(...) method. For example:

# app/graphql/types/base_input_object.rb
# Add a base class
class Types::BaseInputObject < GraphQL::Schema::InputObject
end

class Types::PostAttributes < Types::BaseInputObject
  description "Attributes for creating or updating a blog post"
  argument :title, String, "Header for the post"
  argument :full_text, String, "Full body of the post"
  argument :categories, [Types::PostCategory], required: false
end

For a full description of the argument(...) method, see the argument section of the Objects guide.

Using Input Objects

Input objects are passed to field methods as an instance of their definition class. So, inside the field method, you can access any key of the object by:

calling its method, corresponding to the name (underscore-cased)
calling #[] with the camel-cased name of the argument (this is for compatibility with previous GraphQL-Ruby versions)

class Types::MutationType < GraphQL::Schema::Object
  # This field takes an argument called `attributes`
  # which will be an instance of `PostAttributes`
  field :create_post, Types::Post, null: false do
    argument :attributes, Types::PostAttributes
  end

  def create_post(attributes:)
    puts attributes.class.name
    # => "Types::PostAttributes"
    # Access a value by method (underscore-cased):
    puts attributes.full_text
    # => "This is my first post"
    # Or by hash-style lookup (camel-cased, for compatibility):
    puts attributes[:fullText]
    # => "This is my first post"
  end
end

Customizing Input Objects

You can customize the GraphQL::Schema::Argument class which is used for input objects:

class Types::BaseArgument < GraphQL::Schema::Argument
  # your customization here ...
end


class Types::BaseInputObject < GraphQL::Schema::InputObject
  # Hook up the customized argument class
  argument_class(Types::BaseArgument)
end

You can also add or override methods on input object classes to customize them. They have two instance variables by default:

@arguments: A GraphQL::Execution::Interpreter::Arguments instance
@context: The current GraphQL::Query::Context

Any extra methods you define on the class can be used for field resolution, as demonstrated above.

Converting to Other Ruby Objects

Your input objects can be automatically converted to other Ruby types before they’re passed to your application code. This is an easy way to use Range’s in your schema:

class Types::DateRangeInput < Types::BaseInputObject
  description "Range of dates"
  argument :min, Types::Date, "Minimum value of the range"
  argument :max, Types::Date, "Maximum value of the range"

  def prepare
    min..max
  end
end

class Types::CalendarType < Types::BaseObject
  field :appointments, [Types::Appointment], "Appointments on your calendar", null: false do
    argument :during, Types::DateRangeInput, "Only show appointments within this range"
  end

  def appointments(during:)
    # during will be an instance of Range
    object.appointments.select { |appointment| during.cover?(appointment.date) }
  end
end

`@oneOf`

You can make input objects that require exactly one field to be provided using one_of:

class FindUserInput < Types::BaseInput
  one_of
  # Either `{ id: ... }` or `{ username: ... }` may be given,
  # but not both -- and one of them _must_ be given.
  argument :id, ID, required: false
  argument :username, String, required: false
end

An input object with one_of will require exactly one given argument and it will require that the given argument’s value is not nil. With one_of, arguments must have required: false, since any individual argument is not required.

When you use one_of, it will appear in schema print-outs with input ... @oneOf and you can query it using { __type(name: $typename) { isOneOf } }.

This behavior is described in a proposed change to the GraphQL specification.