Example of creating a service class in Rails that uses exception raising

Service Layer Example.rb

class Gl::TransactionsController < ApplicationController
  def new
  end

  def create
    teller = Gl::TellerService.new()
    response = teller.transfer_funds(params)
    if response.successful?
      @transactions = response.data
      respond_with @transactions
    else
      flash[:error] = response.errors.join(", ")
      redirect_to gl_accounts_url and return false
    end
  end
end

class Gl::TellerService

  def transfer_funds(options)
    source_account      = Gl::Account.where(:id => options[:source_account_id]).first
    destination_account = Gl::Account.where(:id => options[:account_id]).first
    return ServiceResponse.error("Source Account not found!") if source_account.blank?
    return ServiceResponse.error("Destination Account not found!")   if destination_account.blank?
    return ServiceResponse.error("Amount must be specified and > 0") if options[:amount].blank? || options[:amount] <= 0
    period = period_for_transaction(source_account.company, options[:transaction_date] || Time.now)
    if period.blank?
      return ServiceResponse.error("GL Period not found for the specified transaction date.")
    end
    options.merge! period
    source_transaction      = create_transaction(source_account, options, !source_account.debit_account?)
    destination_transaction = create_transaction(destination_account, options, destination_account.debit_account?)

    begin
      Gl::Account.transaction do
        source_transaction.save!
        destination_transaction.save!
      end
    rescue ActiveRecord::RecordInvalid
      return ServiceResponse.error("Invalid Transaction Records")
    end
    return ServiceResponse.success([source_transaction, destination_transaction])
  end

private
  def period_for_transaction(company, transaction_date=Time.now)
    if company.use_gl_periods
      period = Gl::Period.where(:company_id => self.company_id).where(["start_date >= :transaction_date AND end_date < :transaction_date",{:transaction_date => transaction_date}]).first
      return nil if period.blank?
      return {:gl_period => period.period_number, :gl_period_year => period.period_year}
    else
      {:gl_period => transaction_date.month, :gl_period_year => transaction_date.year}
    end
  end

  def create_transaction(account, options, debit)
    transaction = account.transactions.new(:gl_period => options[:gl_period],:gl_period_year => options[:gl_period_year], :transaction_date => options[:transaction_date] || Time.now,:memo => options[:memo],:source => options[:source] ? options[:source] : "Manual")
    if debit
      transaction.debit = options[:amount]
    else
      transaction.credit = options[:amount]
    end
    return transaction
  end
end