From: jake kaiden <jakekaiden@...>
Date: 2011-04-15T12:30:28+09:00
Subject: Re: Understanding global variables.

hi fily,

  as 7stud says, the "@" variables are not global, but instance
variables - which means you can pass them between methods (very handy.)
from what i gather of what you're trying to do with what you've written,
i don't think you actually need instance variables at all, take a look
at this for example:

#####
class Car
  def go(mil_gal, fuel_gal)
  mileage = mil_gal * fuel_gal
  puts mileage
  end
end

car = Car.new
car.go(10, 50)
#=> 500
#####

    or you could do something like this:

#####
class Car
def initialize(mil_gal, fuel_gal)
  mileage = mil_gal * fuel_gal
  puts mileage
end
end

car = Car.new(10, 50)
#=> 500
car = Car.new(30,70)
#=> 2100
###

  if you want to use instance variables, you can do something like this:

#####
class Car

  def initialize
  @mil_gal = 10
  @fuel_gal = 50
  end

  def go(mil_gal, fuel_gal)
  @mil_gal = mil_gal
  @fuel_gal = fuel_gal
  self.mileage
  end

  def mileage
  mileage = @mil_gal * @fuel_gal
  puts mileage
  end

end

car = Car.new
car.mileage
#=> 500
car.go(30, 70)
#=> 2100
####

  and if you want to pass those instance variables outside of the class,
and be able to change them, you can do something like this:

#####
class Car

attr_accessor :mil_gal, :fuel_gal, :mileage

def initialize
  init_mil_gal = 10
  init_fuel_gal = 50
  self.go(init_mil_gal, init_fuel_gal)
end

def go(mil_gal, fuel_gal)
  @mil_gal = mil_gal
  @fuel_gal = fuel_gal
end

def mileage
  @mileage = @mil_gal * @fuel_gal
end

end

car = Car.new
puts car.mil_gal, car.fuel_gal, car.mileage
puts
car.go(30, 70)
puts car.mil_gal, car.fuel_gal, car.mileage
car.mil_gal = 38
puts
puts car.mil_gal
puts car.mileage
#####


  drive on,
  - j

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