Apply alias for loop in grape entity

Question

I would like to get the following JSON.

[{"Product":{"CountryName":4848, }},{"Product":{"CountryName":700}]


module API
  module Entities
    class Example < Grape::Entity
      expose(:product) do
        expose(:country_name) do |product, options|
          product.country.name
        end
      end
    end
  end
end

The parameters are product and name. I would like to return Product, ProductName.

How to apply alias for looping elements in grape entity framework?

Answer 1

• Product attribute : use a 'Product' string instead of the :product symbol,
• CountryName attribute : you need to create a method in your entity that will return product.country.name and expose it in your entity. And then, use an alias so that the key will be CountryName as expected (you can see grape-entity documentation about aliases if need be).

In your case, this would give :

module API
  module Entities
    class Product < Grape::Entity
      expose 'Product' do
        # You expose the result of the country_name method, 
        # and use an alias to customise the attribute name
        expose :country_name, as: 'CountryName'
      end

      private

      # Method names are generally snake_case in ruby, so it feels
      # more natural to use a snake_case method name and alias it
      def country_name
        object.country.name
      end
    end
  end
end

And in your endpoint, you specify the entity that must be used to serialize the Products instances. In my example, you may have noticed that I took the liberty of renaming the entity to Product, which would give us in the endpoint:

# /products endpoint
resources :products do
  get '/' do
    present Product.all, with: API::Entities::Product
  end
end

Which should get you this kind of output, as expected:

[
    { "Product": { "CountryName": "test 1" } },
    { "Product": { "CountryName": "test 2" } }
]