gistfile1.rb

# initializer
Paysio.api_key = 'test'
Paysio.publishable_key = 'test'

# controller:
class ChargesController < ApplicationController
  def new
    @form = Paysio::Form.new(amount: 3999)
    @form.html_options.merge!(action: charges_path)
  end

  def create
    @form = Paysio::Form.new(amount: 3999)
    @form.html_options.merge!(action: charges_path)
    if params[:payment_system_id]
      @form.values = params
      attributes = {
        amount: '3999',
        currency_id: 'rur',
        description: 'Test charge',
        payment_system_id: params['payment_system_id'],
        success_url: '#SUCCESS_URL#',
        failure_url: '#FAILURE_URL#',
        return_url: '#RETURN_URL#'
      }
      if params[:wallet][:account]
        attributes[:wallet][:account] = params[:wallet][:account]
      end

      begin
        charge = Paysio::Charge.create(attributes)
        @form.add_params(charge_id: charge.id)
      rescue Paysio::Errors::BadRequest => e
        @form.errors = e.params
      end
    end
    render :new
  end
end

# view
= javascript_include_tag "http://code.jquery.com/jquery-latest.min.js"
= javascript_include_tag Paysio.static_url('/paysio.js')
= stylesheet_link_tag Paysio.static_url('/paysio.css')
article
  = @form.render