controller.rb

class MyController < ApplicationController
  
  def create

    params_array_not_supported.each do |offer| # KABOOOM!
       ...
    end 

    offers_params_not_chanaible_with_array.each do |offer_param|
      Offer.new offer_param # ActiveModel::ForbiddenAttributes
    end
    
    offers_params.each do |offer_param|
      Offer.new offer_param # OK
    end
  end
  
  protected
  
  def params_array_not_supported
    params.require(:offers).permit(:amount) #Array does not respond to permit()
  end

  def offers_params_not_chanaible_with_array
      params.require(:offers).each do |offer|
      offer.permit(:amount)
  end
  
  def offers_params
      params.require(:offers).map do |offer|
      offer.permit(:amount)
  end

end

params

"offers"=>[{"amount"=>"5"}, {"amount"=>"5"}]