Rails: Grape swagger array in response attribute

Problem

Using Grapi API, we want to describe an api response containing an object (e.g. User) with an attribute params containing an array of name/value pairs:

module API
  class User < Grape::Entity
    expose :email
    expose :params
  end
  class Param < Grape::Entity
    expose :name
    expose :value
  end
end

How does one do? We've tried: is_array, present_collection, etc. but can't get it to work.

Can't get it to work with the documentation (https://rubydoc.info/github/intridea/grape-entity/Grape/Entity#expose-class_method), since they're using an array `items' at the main level, but we want an array attribute at a secondary level.

Environment

• rails-7.0
• grape-1.7.1

Solution

Credits: https://stackoverflow.com/questions/75230970/rails-grape-swagger-array-example-value-is-showing-as-an-object#76870053

module API
  class User < Grape::Entity
    expose :email
    expose(:params, documentation: { type: API::Param, using: API::Param, is_array: true }) do |uu|
      uu.params
    end
  end

  class Param < Grape::Entity
    expose :name
    expose :value
  end
end

This produces Swagger UI documentation, with a response description like this - params being an array :)

{
  "email": "string",
  "params": [
    {
      "name": "string",
      "value": "string"
    }
  ]
}