Form_for and Rails attributes API

Attributes API allows you to have complex object with specified structure in fields. But how to make forms with this fields?

The answer is pretty simple: you work with them like with nested attributes.

Let’s say, we have class Provider with attribute address.

 class Provider < ApplicationRecord attribute :address, Provider::Address::Type.new, default: Provider::Address.new 

Address has following attributes:

 class Provider::Address extend Dry::Initializer option :country, optional: true option :zip, optional: true option :city, optional: true option :address, optional: true 

Form will look like this:

 = form_for resource_provider, provider_url do |f| = f.fields_for :address do |ff| = ff.label 'Country' = ff.text_field :country, value: @provider.billing_address.country = ff.label 'Zip' = ff.text_field :zip, value: @provider.billing_address.zip = ff.label 'City' = ff.text_field :city, value: @provider.billing_address.city = ff.label 'Address' = ff.text_field :address, value: @provider.billing_address.address 

In controller you have to permit parameters:

 def provider_params params.require(:provider).permit(address: [:city, :zip, :country, :address]) end 

And that’s all. Now, in action method you can assign attributes like this:

 resource_provider.attributes = provider_params resource_provider.save