This pattern is unrestricted; it is used within any architectural layer.
A PED Parameter Object (PO) is a continuation of a pattern in use for twenty years. Martin Fowler said is simply in 1999:
You have a group of [method] parameters that naturally go together; replace them with an object.
The pattern promotes software adaptability; it encourages method signature durability while enabling future functional extensions. That is, you can add values passed to a method without altering the method signature.
Some developers express concern when a PO begins to contain behavior other than accessor/mutator methods. That is, a discomfort with encapsulating logic in a PO that could be placed in a non-PO. To the contrary, Kent Beck clarifies that emerging encapsulation should be encouraged:
“…see if there are bits of code using only the fields in the parameter object you could turn into methods on the parameter object.”
As an aside, POs are a useful pattern for legacy code rescue initiatives.
|Extend Base Class||Optional|
|Static Public Methods (enum)||N|
|Delegate to Helper||N|
- A PO in a multicore context requires intentional design attention.