Sinatra, Datamapper and CouchDB – a trainwreck

Just for purely educational reasons (why not) i decide to combine these three on heroku. The spoiler is already in the title: it didn’t work at all. Datamapper is quite cool and works great with the shared Postgres database, but don’t even bother to get the mongo or couch adapter working. Datamapper seems to gets massively reworked, maybe wait for this to be done and then try again. As for Postgres or MySQL it looks nice.

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Sinatra, Mustache and Heroku – change of plans

Okay, I really like Mustache, it’s clean, it has a reasonably small set of options (conditionals, lists etc.) and has many implementations. One of them being javascript (Mustache.js).
So, i thought what about using Sinatra to generate JSON responses and serving templates, while the client is responsible for the representation. The benefit being a clean RESTful application and a deferred rendering process allowing to play with different options on caching JSON objects and exploring AJAX features.
And above all a fun project.
So, the basic idea:

  1. the root path “/” reads an index html file and hands it out
  2. navigation elements trigger to asynchronous AJAX requests (one for the template, one for the view)
  3. when both are finished mustache.js kicks in and renders the page (or parts of it)

app.rb

get "/" do
  response = File.open("index.html").read
  "#{response}"
end

index.html

...
var template = null;
var view = null;
var templateFinished = false;
var viewFinished = false;

function getTemplate(template){
  [...] xhRequest [...]
  if(request.readyState == 4){
            template = req.responseText;
            templateFinished = true;
            process();
        }
  }

function getView(view){
  [...] xhRequest [...]
  if(request.readyState == 4){
            view = req.responseText;
            viewFinished = true;
            process();
        }
  }

function process(){
  if(templateFinished == true && viewFinished == true){
	document.getElementById("content").innerHTML = Mustache.to_html(template,view);
    }
    else{
        return;
      }
}

So, in my case the rendered stuff replaces the content in the div with the id “content”. To elaborate on that one could pass the id of the element to be replaced as an option to the function and really play with this.