Refactoring: Refactorings/Self Encapsulate Field

Instead of accessing class instance variables directly, create an accessor (getter and setter) method to manipulate the variable.

Mechanics

1. Create a getting and setting method for the field
2. Find all references to the field and replace them with a getting or setting method
3. Double check that you have caught all references
4. Test

Example

Before

class Item
  def initialize(base_price, tax_rate)
    @base_price, @tax_rate = base_price, tax_rate
  end

  def raise_base_price_by(percent)
    @base_price = @base_price * (1 + percent/100.0)
  end

  def total
    @base_price * (1 + @tax_rate)
  end
end

After

class Item
  attr_accessor :base_price, :tax_rate
  def initialize(base_price, tax_rate)
    setup(base_price, tax_rate)
  end

  def setup(base_price, tax_rite)
    @base_price, @tax_rate = base_price, tax_rate
  end

  def raise_base_price_by(percent)
    base_price = base_price * (1 + percent/100.0)
  end

  def total
    base_price * (1 + tax_rate)
  end
end