Refactoring: Refactorings/Move Field

If a field is (or will be) used by another class more frequently than the class in which it is defined, then it should be a field of that class.

Mechanics

1. If you are likely to be moving the methods that access the field frequently or if a lot of methods access the field, it might be better to use Self Encapsulate Field
2. Test
3. Create an attribute reader and a writer (if necessary) in the target class.
4. Determine how to reference the target object from the source

   Note: If an existing field does not already give the target, create a method that will do so. If that still doesn't work, create a new field in the source that can store the target. Try to refactor until this can potentially be removed

5. Replace all references to the source field with references to the appropriate method on the target. Also look in subclasses
6. Test

Example

Before

class Account
  def interest_for_amount_days(amount, days)
    @interest_rate * amount * days / 365
  end
end

class AccountType
  # ...
end

After

class AccountType
  attr_accessor :interest_rate
end

class Account
  def interest_for_amount_days(amount, days)
    @account_type.interest_rate * amount * days / 365
  end
end