Autumn SALE
/ Refactoring / Techniques / Simplifying Method Calls

Preserve Whole Object

Problem

You get several values from an object and then pass them as parameters to a method.

Solution

Instead, try passing the whole object.

Before
int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);
After
boolean withinPlan = plan.withinRange(daysTempRange);
Before
int low = daysTempRange.GetLow();
int high = daysTempRange.GetHigh();
bool withinPlan = plan.WithinRange(low, high);
After
bool withinPlan = plan.WithinRange(daysTempRange);
Before
$low = $daysTempRange->getLow();
$high = $daysTempRange->getHigh();
$withinPlan = $plan->withinRange($low, $high);
After
$withinPlan = $plan->withinRange($daysTempRange);
Before
low = daysTempRange.getLow()
high = daysTempRange.getHigh()
withinPlan = plan.withinRange(low, high)
After
withinPlan = plan.withinRange(daysTempRange)
Before
let low = daysTempRange.getLow();
let high = daysTempRange.getHigh();
let withinPlan = plan.withinRange(low, high);
After
let withinPlan = plan.withinRange(daysTempRange);

Why Refactor

The problem is that each time before your method is called, the methods of the future parameter object must be called. If these methods or the quantity of data obtained for the method are changed, you will need to carefully find a dozen such places in the program and implement these changes in each of them.

After you apply this refactoring technique, the code for getting all necessary data will be stored in one place—the method itself.

Benefits

  • Instead of a hodgepodge of parameters, you see a single object with a comprehensible name.

  • If the method needs more data from an object, you won’t need to rewrite all the places where the method is used—merely inside the method itself.

Drawbacks

  • Sometimes this transformation causes a method to become less flexible: previously the method could get data from many different sources but now, because of refactoring, we’re limiting its use to only objects with a particular interface.

How to Refactor

  1. Create a parameter in the method for the object from which you can get the necessary values.

  2. Now start removing the old parameters from the method one by one, replacing them with calls to the relevant methods of the parameter object. Test the program after each replacement of a parameter.

  3. Delete the getter code from the parameter object that had preceded the method call.