How to use http://dry-rb.org/gems/dry-struct/ and http://dry-rb.org/gems/dry-types/built-in-types/ to ensure params structure

dry.rb

# config/initializers/dry.rb
require 'dry-struct'

module Types
  include Dry::Types.module
end

example.rb

params = {
  pricing_name: String,
  start_date: String,
  end_date: String,
  selected_retailer_ids: [],
  selected_product_ids: [],
  filter_type: String, # percentage, value
  filter_increase: true, # 
  filter_value: Integer, # can be only positive
  manual_prices: [
    {
      retailer_id: Integer,
      product_id: String, # it's product's code
      new_price: Decimal,
    }
  ]
}

# it will ensure the params have valid structure and types for manual prices
manual_prices = params[:manual_prices].map do |manual_price|
  PricingManualPriceEntity.new(manual_price)
end

# we can cast to hash before saving to DB
manual_prices.to_h

pricing_manual_price_entity.rb

# app/entities/pricing_manual_price_entity.rb
class PricingManualPriceEntity < Dry::Struct
  # alternative Types::Coercible::Int will cast string id to int if params have ID as string
  attribute :retailer_id, Types::Strict::Int
  attribute :product_id, Types::String # Product code is a string
  attribute :new_price, Types::Decimal
end