From: Brian Candler <b.candler@...>
Date: 2008-11-11T22:14:27+09:00
Subject: Re: implementing mvc - using observer pattern - beginner to

Adam Akhtar wrote:
> class DB
> ..
> ..
> 
> def insert (task)
> ...
> #some kirybbase calls here.
> ..
> end
> 
> end

In a typical MVC, the model would be a class which represents the task, 
rather than a class which represents the database connection (the latter 
would be hidden away behind it). Hence something like:

  t = Task.new
  t.name = "Paint shed"
  t.save!

...

  t = Task.find_by_name("Paint shed")
  t.completed_at = Time.now
  t.save!

If you only have a DB class, then the controller can talk to it 
directly, but you've lost the "M" from MVC.

This may be no loss - simple models are often dumb and just map directly 
to SQL rows. But sometimes it's useful to put logic in the model layer, 
e.g.

  def full_name
    "#{first_name} #{last_name}"
  end

  def full_name=(name)
    f, l = name.split(" ", 2)
    self.first_name = f
    self.last_name = l
  end

Here we have a virtual accessor that makes it look like the model has a 
full_name column, even though the database actually has two separate 
columns, first_name and last_name.

> class UI
> 
> blahblahblah
> 
> def menu
> puts "|A| to add a task"
> ...
> ...
> end
> 
> def navigation
> menu
> input = gets.chomp
> case input
> when "A"
> add task
> etc
> etc
> etc
> end

If you merge the view into the controller then you might get:

class TasksController
  def list
    tasks = Task.find(:all)
    puts "You have #{tasks.size} tasks"
    tasks.each { |t| puts t.name }
  end

  def show(n)
    task = Task.find(n)
    puts "Showing task #{n}"
    puts t.name
  end

  def create
    print "Enter task name:"
    name = gets.chomp
    print "Enter completion date:"
    date = gets.chomp

    t = Task.new
    t.name = name
    t.date = date
    t.save!
    show(t.id)
  end
end

But what's missing is the sequencing: after showing task n there may be 
associated actions (e.g. edit task n, delete task n, return to listing)

Maybe a good way to approach this is to start as a simple Rails app with 
a sqlite3 backend. Then you can consider how best to build the UI part 
which will (a) show the current view, and (b) prompt for next action.
-- 
Posted via http://www.ruby-forum.com/.