Ruby Best Practices

Transactional Filesystem-Based Data Storage (pstore)

PStore provides a simple, transactional database for storing Ruby objects within a file. This gives you a persistence layer without relying on any external resources, which can be very handy. Using PStore is so simple that I can forgo most of the details and jump right into some code that I use for a Sinatra microapp at work. What follows is a very simple backend for storing replies to an anonymous survey:

class SuggestionBox
  def initialize(filename="suggestions.pstore")
    @filename = filename
  end

  def store
    @store ||= PStore.new(@filename)
  end

  def add_reply(reply)
    store.transaction do
      store[:replies] ||= []
      store[:replies] << reply
    end
  end

  def replies(readonly=true)
    store.transaction do
      store[:replies]
    end
  end

  def clear_replies
    store.transaction do
      store[:replies] = []
    end
  end
end

In our application, the usage of this object for storing responses is quite simple. Given that box is just a SuggestionBox in the following code, we just have a single call to add_reply that looks something like this:

box.add_reply(:question1 => params["question1"],
              :question2 => params["question2"])

Later, when we need to generate a PDF report of all the replies in the suggestion box, we do something like this to extract the responses to the two questions:

question1_replies = []
question2_replies = []
box.replies.each do |reply|
  question1_replies << reply[:question1]
  question2.replies << reply[:question2]
end

So that covers the usage, but let’s go back in a ...