Replace Parameter with Explicit Methods

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Latest revision as of 12:29, 26 September 2009

This is used when you have a method which switches it's functionality based on a passed in parameter.

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-== Motivation ==
+This is used when you have a method which switches it's functionality based on a passed in parameter.
-''Refactoring'' [[Martin Fowler 1999]] states that: "If a method can get a value that is passed in as a parameter by another means, it should."
+==Steps==
+* Create a new method for each case
+* Replace all calls to the old method with a call to the relevant new one
+* Delete the old method
-== Example ==
+==References==
+* [http://sourcemaking.com/refactoring/replace-parameter-with-explicit-methods]
-An object invokes a method, then passes the result as a parameter for a method. The receiver can also invoke this method. So the best idea is to remove the parameter and let the receiver invoke the method.
- int basePrice = quantity * itemPrice;
- discountLevel = getDiscountLevel();
- double finalPrice = discountedPrice(basePrice, discountLevel);
-Above we have some code, but lets remove the discountLevel parameter from discountedPrice(basePrice, discountLevel). Now we have:
- int basePrice = quantity * itemPrice;
- double finalPrice = discountedPrice(basePrice);
-The discountedPrice(basePrice) method now looks like:
- discountedPrice(basePrice)
- {
-     int discountLevel = getDiscountLevel();
-     //does calculation type stuff here
-     return discountedPrice;
- }