This is a not a comparison of features. We really like Rails and we took some ideas from it.
The purpose of this document is to teach web2py to Rails programmer.
Rails is based on Ruby, web2py is based on Python
In Rails:
rails MyProject
In web2py
web2py.py -S MyProject
or, even better, use the web based administrative interface to create, deploy, manage, and edit projects.
The provided web2py admin works like heorku.com for Rails but provides more functionality than heroku.
In Rails
def world
@greeting = "hello world!"
end
In web2py
def world():
return dict(greeting="hello world!")
In Rails variables to passed to the view start with @, in web2py they are explicitly returned in a dictionary.
Notice that in Rails you get a template missing error. In web2py you don't, you get a generic template render the message variable without complaints.
In Rails
<html><body>
<% 16.times do |i| %>
<%= @greeting %> <%= i %><br/>
<% end %>
</body></html>
In web2py
<html><body>
{{ for i in range(16): }}
{{= greeting }} {{= i }}<br/>
{{ pass }}
</body></html>
In Rails
class AddTable < ActiveRecord::Migration
def self.up
create_table :user do |t|
# id is created for us.
t.column :name, :string, :limit => 50, :null => false
end
end
def self.down
drop_table :user
end
end
In web2py
db=SQLDB('sqlite://mydb.db')
db.define_table('user',
SQLField('name',lenght=50))
Notice that:
To select and delete a user in Rails
User.find(@params['id']).destroy
The same code in web2py is
db(db.user.id==request.vars.id).delete()
In web2py form variables are in request.vars and they can be accessed by
request.var.myvariable or request.vars['myvariable']
The first notation returns None if not request.vars.has_key('myvariable'). The second raises an exception. You can use request.post_vars to get only post vars and request.get_vars to get only get variables.
To store stuff in session you do
session.myvariable=3
and you retrieve it with
myvariable=session.myvariable
The response object is used to stream data, create xmlrpc services and send some standard variables to the views
In Rails
redirect_to :action => 'list'
In web2py
redirect('list')
Not native in Rails.
In web2py:
T('this is a message')
(and as usual no need to import anything since you are supposed to use T) You web2py you can also do
T('this is message %(name)s',dict(name='xxx'))
it-it.py ) in the admin interface.In Rails
<%= link_to "Create", :action => "new" %>
In web2py helpers have the same names as the corresponding HTML
{{=A('Create',_href=URL(r=request,f='new')}}
produces the same output as
<a href="{{=URL(r=request,f='new')}}">Create</a>
Helpers can be nested as in
HTML(BODY(H1('title'),P('bla '*10,_id='main')))
and they can be used to build forms via FORM and INPUT.
Notice that web2py escapes all text displayed in views to prevent XSS. Only text marked by XML('...') is not escaped.
Rails comes with Scriptaculous. web2py comes with jQuery base. But with any of them you can use any JS library.
In Rails:
require 'json/objects'
def MyController < ApplicationController
def give_me_json
...
render :text => data.to_json
end
end
In web2py
import gluon.contrib.simplejson as sj
def give_me_json():
return sj.dumps(dict(pages=pages))
web2py comes in one executable package including an SSL enabled web server, the sqlite database, a web administratve interface that allows you to create/edit/deploy and manage all your applications.
Exception are automatically caught by web2py which logs the traceback, the code causing the exception, and issues a ticket to the visitor that triggered the exception. No code is exposed to the visitor, not even by mistake, ever.
web2py includes libraries for generating CREATE/UPDATE/DELETE forms from your database tables.
web2py includes libraries for handling AJAX, JSON, REST, RSS, ATOM, RTF, CSV, WIKI (markdown) and some more protocols.
web2py has helpers that help you build objects that can be serialized in HTML or XML. Any correct HTML/XML can be generated using exclusively helpers.
web2py code runs on the Google App Engine.
web2py packages everything you need in one binary file that you don't even need to install. I keep mine on a USB stick. You just click on it and it start web server, the sqlite database, fires the browser for access to the administrative interface.
web2py deals with static files for you, streams them when they are large (both in upload and download), and automatically supports IF_MODIFIED_SINCE and PARTIAL CONTENT. You can do streaming audio and video without any extra tools or settings.
web2py can map URLs using regular expressions so that you can use it to handle legacy URLs.
web2py has no configuration files. You just create an empty app via the shell or the web based admin interface and create/edit your models, controllers and views (using an editor or the web based admin interface).
There is a repository of free web2py apps here and an interactive FAQ there.