Upcase Refactoring Trail

Replace Variable with Query

Refactoring exercise using the Replace Temp with Query refactoring for the Upcase Refactoring Trail.

Replace Temp with Query

Extract the expression into a method. Replace all references to the temp with the expression. The new method can then be used in other methods. -- Martin Fowler

Before

class Tipper
  ...

  def total
    tax_amount      = amount * TAX
    discount_amount = amount * (discount_percentage / 100.0)
    tip_amount      = amount * (tip_percentage / 100.0)

    amount + tax_amount - discount_amount + tip_amount
  end
end

After

class Tipper
  ...

  def total
    amount + tax_amount - discount_amount + tip_amount
  end

  private

  def tax_amount
    amount * TAX
  end

  def discount_amount
    amount * (discount_percentage / 100.0)
  end

  def tip_amount
    amount * (tip_percentage / 100.0)
  end
end

Additional Resources

• Ruby Patterns: Query Method by Rein Henrichs