From: Michael Sung <lists@...>
Date: 2012-06-13T04:04:26+09:00
Subject: Question on If @Instance Statements

I have another Chris Pine "Learning Programming" Question.  I'm almost
finished with the book but became confused on his use of "If"
statements.

QUESTION: In the below code snippet, why does he use "if @asleep"
instead of just writing "passageOfTime", "puts", and then, "if @asleep =
false"?

This is the same question I have for other parts of the program that use
"if @asleep" so I guess clarifying this will help me understand how it
is being used.  Thanks!


def putToBed
    puts 'You put ' + @name + ' to bed.'
    @asleep = true
    3.times do
      if @asleep
        passageOfTime
      end
      if @asleep
        puts @name + ' snores, filling the room with smoke.'
      end
    end
    if @asleep
      @asleep = false
      puts @name + ' wakes up slowly.'
    end
  end



FULL PROGRAM FOLLOWS BELOW:

class Dragon

  def initialize name
    @name = name
    @asleep = false
    @stuffInBelly     = 10  #  He's full.
    @stuffInIntestine =  0  #  He doesn't need to go.

    puts @name + ' is born.'
  end

  def feed
    puts 'You feed ' + @name + '.'
    @stuffInBelly = 10
    passageOfTime
  end

  def walk
    puts 'You walk ' + @name + '.'
    @stuffInIntestine = 0
    passageOfTime
  end

  def putToBed
    puts 'You put ' + @name + ' to bed.'
    @asleep = true
    3.times do
      if @asleep
        passageOfTime
      end
      if @asleep
        puts @name + ' snores, filling the room with smoke.'
      end
    end
    if @asleep
      @asleep = false
      puts @name + ' wakes up slowly.'
    end
  end

  def toss
    puts 'You toss ' + @name + ' up into the air.'
    puts 'He giggles, which singes your eyebrows.'
    passageOfTime
  end

  def rock
    puts 'You rock ' + @name + ' gently.'
    @asleep = true
    puts 'He briefly dozes off...'
    passageOfTime
    if @asleep
      @asleep = false
      puts '...but wakes when you stop.'
    end
  end

  private

  #  "private" means that the methods defined here are
  #  methods internal to the object.  (You can feed
  #  your dragon, but you can't ask him if he's hungry.)

  def hungry?
    #  Method names can end with "?".
    #  Usually, we only do this if the method
    #  returns true or false, like this:
    @stuffInBelly <= 2
  end

  def poopy?
    @stuffInIntestine >= 8
  end

  def passageOfTime
    if @stuffInBelly > 0
      #  Move food from belly to intestine.
      @stuffInBelly     = @stuffInBelly     - 1
      @stuffInIntestine = @stuffInIntestine + 1
    else  #  Our dragon is starving!
      if @asleep
        @asleep = false
        puts 'He wakes up suddenly!'
      end
      puts @name + ' is starving!  In desperation, he ate YOU!'
      exit  #  This quits the program.
    end

    if @stuffInIntestine >= 10
      @stuffInIntestine = 0
      puts 'Whoops!  ' + @name + ' had an accident...'
    end

    if hungry?
      if @asleep
        @asleep = false
        puts 'He wakes up suddenly!'
      end
      puts @name + '\'s stomach grumbles...'
    end

    if poopy?
      if @asleep
        @asleep = false
        puts 'He wakes up suddenly!'
      end
      puts @name + ' does the potty dance...'
    end
  end

end

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