From: Jason Lillywhite <jason.lillywhite@...>
Date: 2009-01-23T00:40:40+09:00
Subject: Design question: class methods verses initialize

I have a design question for a beginner:

what is better for my case?
I want to access functionality from a library I created.
I've tried class methods like this:

class Calc
  def Calc.velocity_head(v)
    v**2/(2.0*G)
  end
  def Calc.pressure_head(p)
    h = p / Gamma
  end
  def etc...
end

This is nice because now I can create many "velocity_head" objects or
"pressure_head" objects as needed by doing vh1 = Calc.velocity_head(4.5)
for example. But what if I have a bunch of methods in a class that all
require the same exact arguments? My first thought was using initialize
and instance variables:

Class Geom
  def initialize(b, y, m)
    @b, @y, @m = b, y, m
  end
  def area
    @a = (@b + @m * @y) * @y
  end
  def hyd_rad
    @r = (@b + @m * @y) * @y / (@b + 2.0 * @y * (1 + @m**2)**0.5)
  end
  def wet_perim
    @p = @b + 2.0 * @y * (1.0 + @m**2)**0.5
  end
  def etc...
end

But now I have to do area1 = Geom.new(4, 1.5, 2) and then area1.area
Is this the only other way to do this:?

Class Geom
  def Geom.area(b, y, m)
    a = (b + m * y) * y
  end
  def Geom.hyd_rad(b, y, m)
    r = (b + m * y) * y / (b + 2.0 * y * (1 + m**2)**0.5)
  end
  def Geom.wet_perim(b, y, m)
    p = b + 2.0 * y * (1.0 + m**2)**0.5
  end
  def etc...
end

I feel like I'm re-stating the arguments more than necessary. Could
someone give me some pointers? Thank you!
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