Something strange with CLASS and SCOPE

ruby-talk
1

There is onething regarding class and scope I felt puzzled for a while.
Below is my code.

class QQ
  @strange=Array.new
  def report
    puts @strange.class
  end
end

q=QQ.new
q.report

method of a specific instance. However, if I initialize the "@strange"
array in the very begining of my class. In my method, I will derive a
NilClass. That means, there is something to do with scope. It seems that
every block would produce a local scope.

So, how can I overcome such deliemma. I want an Array that can be used
by every method in the class. Thank you in advance.

···

From my understanding, instance variable should be available to every
--
Posted via http://www.ruby-forum.com/.

2

There is onething regarding class and scope I felt puzzled for a while.
Below is my code.

class QQ
  @strange=Array.new
  def report
    puts @strange.class
  end
end

q=QQ.new
q.report

From my understanding, instance variable should be available to every
method of a specific instance. However, if I initialize the "@strange"
array in the very begining of my class. In my method, I will derive a
NilClass. That means, there is something to do with scope. It seems that
every block would produce a local scope.

The array you're setting is an instance variable on the Class instance
called QQ. You want an instance variable for each new instance of QQ.

So, how can I overcome such deliemma. I want an Array that can be used
by every method in the class. Thank you in advance.

    class QQ
      def initialize
        @strange=Array.new
      end

      def report
        puts @strange.class
      end
    end
    
    q=QQ.new
    q.report

···

On Sat, Jan 09, 2010 at 03:57:33AM +0900, Tony Tony wrote:

--
Aaron Patterson
http://tenderlovemaking.com/

3

Only if your instance variables have been initialized, like so:

class QQ
   def initialize # Used by Ruby when you do "QQ.new"
     @array = Array.new
   end

   def report
     puts @array.class
   end
end

q = QQ.new
q.report

(Actually, the class instance gets initialized, and not the instance variables, strictly speaking.)

···

On 08.01.2010 19:57, Tony Tony wrote:

There is onething regarding class and scope I felt puzzled for a while.
Below is my code.

class QQ
   @strange=Array.new
   def report
     puts @strange.class
   end
end

q=QQ.new
q.report

From my understanding, instance variable should be available to every
method of a specific instance

--
Phillip Gawlowski

4

Phillip Gawlowski wrote:

(Actually, the class instance gets initialized, and not the instance
variables, strictly speaking.)

It's worth mentioning that a class is itself an object (an instance of
class Class), and therefore has its own instance variables.

class QQ
  # at this point, the current object ('self') is class QQ itself
  @strange=Array.new

  def report
    # but here, the current object is an instance of class QQ
    # so this is an instance variable in a different object
    puts @strange.class
  end
end

Sometimes the class itself is a useful place to store values:

class QQ
  @count = 0

  def self.count
    @count
  end

  def self.count=(x)
    @count = x
  end

  def initialize
    self.class.count = self.class.count + 1
  end
end

a = QQ.new
b = QQ.new
puts "You have created #{QQ.count} QQ's"

···

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