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scratch/content/html/en/blog/mvc/mvc4.md
Yann Esposito (Yogsototh) 3e4d181219 New rules (use md), old filters, intensedate css
2010-03-12 13:49:27 +01:00

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filters_pre kind menupriority title multiTitle
bluecloth
article 4 MVC explained (make it usable)
fr en
make it usable make it usable

Make it usable

The app is almost usable. You only need to have a way to add new tasks and to delete them. Let's do it using

http://localhost:2000/?newtask="new task text" http://localhost:2000/?deletetask=taskNumber

It is not a so difficult part, you only need a little code in the do_GET function of server to call to correct Todo methods depending of the request.

And of course code the correponding method in the Todo class.

#!/usr/bin/env ruby

require 'webrick'

the Todo class is in an external file

require 'todo.rb' include WEBrick

s = HTTPServer.new( :Port => 2000 )

class Servlet # you write the common header and footer of all pages # directly in the source code @@Header='

<html xmlns="http://www.w3.org/1999/xhtml" lang="fr" xml:lang="fr"> <head> </head>
' @@Footer='
' 
def initialize()
    @todo=Todo.new
end

# implement the GET request
def do_GET(req, res)
    if req.query['newtask']
        @todo.addTask(req.query['newtask'])
    elsif req.query['deletetask']
        @todo.deleteTask(req.query['deletetask'])
    end
    res.body = @@Header + @todo.content + @@Footer
    res['Content-Type'] = "text/html"
end

end

servlet=Servlet.new s.mount_proc("/"){ |req,res| servlet.do_GET(req,res) }

trap("INT"){ s.shutdown } s.start

Where the TODO class is really simple and coded like this:

<code class="ruby" file="todo.rb">

class Todo def initialize @todoList=['first task','second task'] end def content res='

Todo

    '; i=0 @todoList.each do |task| res<<='
  • '+task+ ' done'+'
    • ' i+=1 end res<<='
Task: ' return res end def addTask(task) @todoList<<=task end def deleteTask(taskNum) @todoList.delete_at(Integer(taskNum.to_s)) end

end

Here is the results :

A screenshot of this minimal application

Now we have separated the server and the todo list into two different files.

The application's working within only 76 lines of code

Now speak about the problems of this (working) implementation.

What will occurs if you want to change from list to tables for example or more generally if we want to change the html structure?

You'll have to modify the Todo class.

This is why you should separate even more each concepts.