From: Brian Candler <b.candler@...>
Date: 2010-03-29T17:27:44+09:00
Subject: Re: Read & Write data on a site

Jose Wong wrote:
> Ok, so I will choose MySQL and Ruby. Is there a tutorial for MySQL 
> queries using Ruby?

Type "ruby mysql" into google. The fifth result is this:
http://www.kitebird.com/articles/ruby-mysql.html

That's writing code using the MySQL API directly.

If you prefer to go via a thin abstraction layer so that your code can 
talk to other databases too, try "ruby dbi". I listed some 
object-oriented APIs earlier.

> If all I want was just to have a simple place to read and write ruby 
> variables, is it really necessary to have a web framework? Is there some 
> kind of simple service that allows that? All I want is... Well, store 
> data somewhere.

Well, think about how the web works.

1. A client clicks on a link, or clicks a submit button on a form
2. The client makes a HTTP GET or POST request to a web server
3. The web server generates some HTML and returns it to the client

What you need is a way for the generated HTML to depend on the contents 
of your database. Web frameworks give you an easy way to do this. For 
example with Sinatra you can write

  get '/' do         # <-- match incoming URL
    "hello world"    # <-- returned data
  end

Sinatra runs under Rack, a generic API for connecting ruby web servers 
to ruby applications. This means there are lots of ways to run your 
application without modifying the code - as a standalone server 
listening on a port, under Apache using Phusion Passenger, as a fastcgi 
etc.

I'd recommend this approach as both quick to get started and yet very 
flexible as you grow.

If you don't want to do this for any reason, the main alternatives are:

1. CGI - the web server will start a ruby interpreter with your script 
when the incoming request arrives, setting information about the request 
in environment variables. Google "ruby cgi" for examples.

2. eruby/erb - you write a HTML page with ruby embedded directly in it, 
PHP-style. It's possible to configure a web server to serve this 
directly.

CGI is inefficient because a new ruby interpreter is started for each 
incoming request. You can make it persistent using fastcgi or scgi. 
eruby/erb needs your web server specially configuring and can have 
problems with one page being able to pollute the environment used by 
another page.

HTH,

Brian.
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