preserve-whole-object.md

Preserve Whole Object

This refactoring changes the interface of a method.

It applies when you often find yourself pulling individual fields out of some object to pass them to the method as separate arguments.

It would be better to pass the whole object to the method, so the knowledge of how to get the data out of the object can live in one place.

Example

Before

def record(amount, payment_type, cardholder)
  # ...
end

purchase = # ...
record(
  purchase.amount,
  purchase.payment_type,
  purchase.cardholder
)

After

def record(purchase)
  amount = purchase.amount
  payment_type = purchase.payment_type
  cardholder = purchase.cardholder
  # ...
end

purchase = # ...
record(purchase)

Next Steps

Often, this refactoring reveals Feature Envy. If the method knows about the data fields of an object, maybe it should live on that object.