gistfile1.rb

# There are 3 ways to access the value of an instance variable: 
# @var, the getter method (eg: var), and self.var (where self is the instance itself)
class Car
  attr_accessor :color

  def shade
    "Some kind of #{@color}."
  end

  def hue
    "Looks totally #{color}ish."
  end

  def style
    "Very #{self.color}tastic!"
  end
end

>> c = Car.new
=> #<Car:0x10a3642b8>
>> c.color = "blue"
=> "blue"
>> c.shade
=> "Some kind of blue."
>> c.hue
=> "Looks totally blueish."
>> c.style
=> "Very bluetastic!"

# If we override the getter method created by attr_accessor, we 
# see the difference in @var and self.var (which is really a call to the getter method)
class Car
  attr_accessor :color

  def shade
    "Some kind of #{@color}."
  end

  def hue
    "Looks totally #{color}ish."
  end

  def style
    "Very #{self.color}tastic!"
  end

  def color
    @color.upcase
  end
end

>> c = Car.new
=> #<Car:0x10a392c08>
>> c.color = "blue"
=> "blue"
>> c.color
=> "BLUE"
>> c.shade
=> "Some kind of blue."
>> c.hue
=> "Looks totally BLUEish."
>> c.style
=> "Very BLUEtastic!"

# But what if we are setting a local instance variable with the exact same name?
class Car
  attr_accessor :color

  def shade
    color = "red"
    "Some kind of #{@color}."
  end

  def hue
    color = "red"
    "Looks totally #{color}ish."
  end

  def style
    color = "red"
    "Very #{self.color}tastic!"
  end

  def color
    @color.upcase
  end
end

>> c = Car.new
=> #<Car:0x10a3c0018>
>> c.color = "blue"
=> "blue"
>> c.color
=> "BLUE"
>> c.shade
=> "Some kind of blue."
>> c.hue
=> "Looks totally redish."
>> c.style
=> "Very BLUEtastic!"