I'd like to share some more knowledge and the concrete implementation I did for my specific problem.
The software I'm working on is a personal finance web app and to make the sign-up process and first steps as easy as possible, I'm using programmatic templates that I can use to fill out a few forms during sign-up. The users will have several of those templates to choose from.
I shorted the code a little bit in functionality and it's MIT licensed if you want to use it.
Let's start with the data input file, it is Ruby code and extremely easy to read and understand:
ledger "Ledger for #{Date.today.year}" do
unit '€'
# Looks verbose, but the first it the name, the second argument the type.
# The app is in German so the name would differ there
account 'Equity', 'equity'
account 'Assets', 'assets'
account 'Expenses', 'expenses'
account 'Income', 'income'
account 'Liabilities', 'liabilities'
transaction 'Bank account' do
date Date.today
entry 'Equity:Current', -200
entry 'Assets:Bank:Current'
end
transaction 'Car credit' do
entry 'Equity:Car', 5000
entry 'Liabilities:Car'
end
recurring_transaction 'Health Insurance', monthly: 3, day_of_month: 15 do
entry 'Assets:Bank:Current', -1550
entry 'Expenses:Insurance'
end
recurring_transaction 'Job', weekly: 2, day: :tuesday do
entry 'Income:Job', -2350
entry 'Assets:Bank:Current'
end
recurring_transaction 'Rent', monthly: 1, day_of_month: -2 do
entry 'Expenses:Living:Rent', 650.23
entry 'Assets:Bank:Current'
end
recurring_transaction 'Envolopes', weekly: 1, day: :monday do
entry 'Expenses:Food', 40
entry 'Expenses:Fun', 20
entry 'Expenses:Other', 30
entry 'Assets:Bank:Current'
end
recurring_transaction 'Savings', monthly: 1, day_of_month: 1 do
entry 'Assets:Bank:Savings', 75
entry 'Assets:Bank:Current'
end
recurring_transaction 'Ratenkredit', monthly: 1, day_of_month: 1 do
entry 'Liabilities:Car', 350
entry 'Assets:Bank:Current'
end
end
And this is the TemplateProcessor that handles those input files and processes them into a Ledger with transactions, recurring transactions and accounts. Obviously there are some data models for Ledger, Transaction etc, in my case I'm using MongoId but the DSL is independent of this. My extended version of the TemplateProcessor also has a few lines for dry runs where no data is stored.
You can clearly see the instance_eval running the inner block for ledger and transaction.
Calls from the input file like date and unit are passed on to the respective objects via method_missing
require 'cleanroom'
module TemplateProcessor
def self.process(template, user, ledger = nil)
dsl = DSL.new
dsl.user = user
dsl.ledger = ledger
dsl.evaluate(template)
end
class DSL
attr_accessor :user
attr_accessor :ledger
attr_accessor :ledgers
def method_missing(method, *args)
if @transaction && @transaction.respond_to?(method)
@transaction.send("#{method}=", *args)
return
end
@ledger.send("#{method}=", *args)
end
def ledger(name, &block)
@ledger ||= Ledger.new(name: name)
@ledger.ledger_roles.new(creator: user, user: user)
@ledger.save!
instance_eval(&block)
@ledgers ||= []
@ledgers.push @ledger
@ledger = nil
end
expose :ledger
def account(name, account_type)
account = @ledger.accounts.new(name: name, account_type: account_type)
account.save!
end
def transaction(description, &block)
@transaction = @ledger.transactions.new(description: description)
@transaction.date = Date.today
@amount = 0
instance_eval(&block)
@transaction.save!
@transaction = nil
end
expose :transaction
def entry(account_name, amount = nil)
if amount.nil?
amount = - @amount
@amount = 0
else
@amount += amount
end
@transaction.entries.new(account_name: account_name, amount: amount)
end
expose :entry
def recurring_transaction(description, rule, &block)
@transaction = @ledger.recurring_transactions.new(description: description)
@transaction.rule = IceCube::Rule
rule.each_pair do |method, args|
@transaction.rule = @transaction.rule.send(method, *args)
end
@amount = 0
instance_eval(&block)
@transaction.save!
@transaction = nil
end
expose :recurring_transaction
end
end
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