From: Todd Benson <caduceass@...>
Date: 2007-06-14T02:22:04+09:00
Subject: Re: Generate a grid of cells, and give characteristics

On 6/13/07, Joop Van den tillaart <tillaart36@hotmail.com> wrote:

> Do i need to put this array in some sort of database? So i get to have
> some columns where one column represents the cells numbers 1..196 some
> other columns then need to have some cell characteristics, and with
> these characteristics and a formula (which i already have) the cell
> types need to be assigned (infrastructure, housing, facilities etc.)

What's your motivation?  To just get it done and working (I'm a little
confused as to what "it" is, though)?  To learn Ruby or OOP?  Is this
a one-off (used just for this) or to be expanded and used for
something else (are you building a script or an app, for example)?
Are you automating data construction, manipulation, or evaluation, or
all of the above?  You say you have formulas for characteristics of
the each of the 196 "plots".  Do these formulas depend solely on x and
y coordinates (i.e. all plots with x == 4 have a creek running through
them, all plots with y == 13 are next to power lines, etc.) or do you
plug this info in for each plot one at a time?  Is it permanent info?

Should you use a database?  It depends.  I'm a database freak, so I
probably would use one even if it required some extra effort (but I'm
well versed in SQL, so that part would be easy; there are some DB
engineers out there that would be more than happy to encode your
application entirely in the DB, complete with distance calculations,
autogeneration of street addresses, the whole works!  But that's no
fun ... more like trying to fit a square peg in a round hole.

By the sound of it so far, I'd start with a database containing the
unique and rare characteristics of each plot and then "script" into
the DB the more general characteristics using SQL and/or Ruby.  Then
I'd build some generic classes so that I can alter data in the
database, maybe a Site class (of which you will have only one
instance), a Plot class, a Road class, etc.  If you want to use Ruby
only, I recommend using YAML for your persistent data.  Or, if you
want to stick with a database but avoid SQL, there are some great ORM
and Ruby/SQL bridge tools out there, like ActiveRecord and Sequel
(neither of which I've tried).

There are tons of ways to model this in Ruby; here's one cowboy way I
might try with no regard to an external database -- just playing with
data in the program:

class Plot
  @@neighbors = []
  attr_accessor :x, :y, :characteristics

  def @@neighbors.[]( x, y )
    self.select {|n| n.x==x and n.y==y}.first
  end

  def @@neighbors.used?( x, y )
    self[x,y]
  end

  def < new_chars
    @characteristics.merge! new_chars if new_chars.is_a? Hash
    self
  end

  def self.community
    @@neighbors
  end

  def initialize( x, y )
    raise Exception.new("Property at (#{x},#{y}) already
initialized!") if @@neighbors.used?( x, y )
    @x = x
    @y = y
    @characteristics = {}
    @@neighbors << self
  end

  def to_s
    "Plot <#{@x},#{@y}>: #{@characteristics.inspect}"
  end
end

#####
# Begin little program to play with data

# build a 196 square unit grid of plots
14.times {|x| 14.times {|y| Plot.new(x, y)}}

# grab the plot object at (7,13) with newly defined [] method
# print it two different ways
puts "inspect =>  #{Plot.community[7, 13].inspect}"
puts "puts    =>  #{Plot.community[7, 13]}"

# add some characteristics to a plot using the newly defined < method
# and a hash
puts "After setting some properties:"
puts Plot.community[7, 13] < { :name => "Ruffle Gorge", :electricity => "no" }

# add electricity
puts "After installing electricity:"
puts Plot.community[7,13] < {:electricity => "yes"}

# add a whole new plot off main grid
Plot.new(21,23) < { :name => "Scrooge's Stooge", :water => "no" }
puts "New plot:"
puts Plot.community[21,23]

I'm not suggesting you do something like this ... just to get you
thinking is all.  A more appropriate way would be to have a Site
object that contains Plot objects that know their locations -- like
above, but without @@neighbors, and its methods #[x, y] and #used/
placed in the Site class instead.

Todd