Blueprinter

This guide covers using Typelizer with Blueprinter.

Setup

class ApplicationBlueprint < Blueprinter::Base
  include Typelizer::DSL
end

Fields and Associations

Define fields and associations as usual:

class UserBlueprint < ApplicationBlueprint
  identifier :id
  fields :name, :email
  field :created_at, if: ->(_field, _user, options) { options[:admin] }

  association :posts, blueprint: PostBlueprint
end

Typelizer infers field types from the model (UserBlueprint → User). Use typelize_from when the model name can't be inferred. Fields and associations with if:, unless:, or exclude_if_nil: are optional.

Blueprinter renders an association as a list or a single object depending on the value, so Typelizer asks the model: a has_many association becomes an array. Without a model, set it with typelize:

typelize items: [ItemBlueprint, multi: true]
association :items, blueprint: ItemBlueprint

Computed Fields

Annotate block fields with typelize:

class UserBlueprint < ApplicationBlueprint
  typelize :string
  field :full_name do |user, _options|
    "#{user.first_name} #{user.last_name}"
  end
end

See Manual Typing for full details on the typelize method.

Views

Each view becomes its own type, named after the blueprint and the view:

class UserBlueprint < ApplicationBlueprint
  identifier :id
  fields :name

  view :extended do
    field :email
  end
end

type User = {
  id: number;
  name: string;
}

type UserExtendedView = {
  id: number;
  email: string;
  name: string;
}

An association rendered with a view (association :posts, blueprint: PostBlueprint, view: :summary) uses that view's type.

Limitations

• Transformers (transform, default_transformers) can rename keys at render time, and Typelizer can't see them. For camelCase keys, use Typelizer's properties_transformer.
• default:, field_default, and association_default replace nil at render time, but the types still include | null.
• An association whose blueprint is a proc, or that uses the :identifier view, is typed as unknown.
• root: and meta: are render options, so the generated type describes the blueprint itself, not the wrapper.