Re: to make dot method dot method work?

1. why are you still assigning to @@result?
if i change code1 into code2
code1
class Mycompute
  def initialize(str)
    @str=str
  end
  def values
    @@result=@str
    def @@result.up
      self.upcase
    end
    @@result
  end
  def up
    @@result.upcase
  end
end
code2

class Mycompute
  def initialize(str)
    @str=str
  end
  def values
    @result=@str
    def @result.up
      self.upcase
    end
    @result
  end
  def up
    @result.upcase
  end
end
code2 can  only get  :

 Mycompute.new("Abc").values
=> "Abc"
irb(main):017:0> Mycompute.new("Abc").up
NoMethodError: undefined method `upcase' for nil:NilClass
  from (irb):13:in `up'
  from (irb):17
  from :0
irb(main):018:0> Mycompute.new("Abc").values.up
=> "ABC"
code1 can get
Mycompute.new("Abc").values #=> "Abc"
Mycompute.new("Abc").up #=> "ABC"
Mycompute.new("Abc").values.up #=> "ABC"

2.here is my real code
real code1
require 'rubygems'
require 'mysql'
require 'date'
class  Analyse
  @@result=[]
  def self.vol(symbol,cycle)
  cycle=cycle.to_i
  dbh = Mysql.real_connect("localhost", "root", "******")
  dbh.query("use  stock;")
  result=dbh.query("select symbol,date,open,high,low,close  from 
`#{symbol}` order by date asc;")
  compute=[]
  result.each{|row|   compute<<row.join(";")}
  compute.each.with_index{|row,idx|
  row=row.split(";")
  if idx> cycle-2  then
    if  row[4].to_f==0  then
      row[6]="nil"
    else
      mymax=[]
      mymin=[]
      for  i  in  idx-cycle+1..idx
        mymax<<compute[i].split(";")[3].to_f
        mymin<<compute[i].split(";")[4].to_f
      end
      max=mymax.max
      min=mymin.min
      row[6]=format("%.2f",100*(max-min)/min)
    end
  else
    row[6]="nil"
  end
     @@result<<row.join(";")
   }
   end

def mean
  amean=[]
   @@result.each{|line|
        line.each{|item|
        amean<< item.chomp.split(";")[-1].to_f
       }}
     amean=amean.compact
     format("%.2f",amean.inject(0){|s,n| s+n}/(amean.size.to_f)).to_f
end
end

1)vol method can get  stock Volatility,every  5  day   Volatility,such 
as
 Analyse.vol("c","5")   can get
c;2010-09-09;3.89;3.95;3.88;3.91;4.19
c;2010-09-10;3.92;3.94;3.9;3.91;4.19
c;2010-09-13;3.96;4.01;3.96;3.99;4.97
c;2010-09-14;3.98;3.99;3.91;3.94;4.70
c;2010-09-15;3.92;3.93;3.9;3.92;3.35
c;2010-09-16;3.89;3.98;3.88;3.97;3.35
c;2010-09-17;4;4.02;3.95;3.95;3.61
c is the stock name  ,the last column is  volatility
2)i want  to make  Analyse.vol("c","5").mean  run
real code1 can get :
NoMethodError: undefined method `mean' for nil:NilClass
that is to say ,in real code1
Analyse.vol("c","5")  can get what i want
Analyse.vol("c","5").mean can't
if i change real code1 into real code2 such as:
real code2
require 'rubygems'
require 'mysql'
require 'date'
class  Analyse
  @@result=[]
  def self.vol(symbol,cycle)
  object = Analyse.new
  cycle=cycle.to_i
  dbh = Mysql.real_connect("localhost", "root", "******")
  dbh.query("use  stock;")
  result=dbh.query("select symbol,date,open,high,low,close  from 
`#{symbol}` order by date asc;")
  compute=[]
  result.each{|row|   compute<<row.join(";")}
  compute.each.with_index{|row,idx|
  row=row.split(";")
  if idx> cycle-2  then
    if  row[4].to_f==0  then
      row[6]="nil"
    else
      mymax=[]
      mymin=[]
      for  i  in  idx-cycle+1..idx
        mymax<<compute[i].split(";")[3].to_f
        mymin<<compute[i].split(";")[4].to_f
      end
      max=mymax.max
      min=mymin.min
      row[6]=format("%.2f",100*(max-min)/min)
    end
  else
    row[6]="nil"
  end
     @@result<<row.join(";")
   }
   return object
   end

def mean
  amean=[]
   @@result.each{|line|
        line.each{|item|
        amean<< item.chomp.split(";")[-1].to_f
       }}
     amean=amean.compact
     format("%.2f",amean.inject(0){|s,n| s+n}/(amean.size.to_f)).to_f
end
end
real code2 can get:
 Analyse.vol("c","5")
=> #<Analyse:0xb774af24>
 Analyse.vol("c","5").mean
=> 7.62

what i want is real code3 which can get
1)Analyse.vol("c","5")  can  get output such as
c;2010-09-09;3.89;3.95;3.88;3.91;4.19
c;2010-09-10;3.92;3.94;3.9;3.91;4.19
c;2010-09-13;3.96;4.01;3.96;3.99;4.97
c;2010-09-14;3.98;3.99;3.91;3.94;4.70
c;2010-09-15;3.92;3.93;3.9;3.92;3.35
c;2010-09-16;3.89;3.98;3.88;3.97;3.35
c;2010-09-17;4;4.02;3.95;3.95;3.61
not  => #<Analyse:0xb774af24>
2)Analyse.vol("c","5").mean can get
=> 7.62
not  NoMethodError: undefined method `mean' for nil:NilClass
would you mind to help me to write code3?
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