Saturday, January 14, 2012

long constructor signature vs tons of setters

A mild code smell is a long list of (say 22) constructor parameters to set 22 fields. Alternative is 22 setters.
If some field should be final, then the ctor Pain is justified.

If some of the 22 fields are optional, then it's good to initialize only the compulsory fields in the ctor. Optional fields can use setter.

If one field's initialization is lengthy, then this single initialization can prolong the ctor call, during which the incomplete new-born reference can leak. Therefore, it's perhaps safer to postpone this slow initialization to a setter.

If setter has non-trivial logic for a field, then setter is a reasonable choice.

Best benefit in the ctor route is the final keyword. With setters, we need to deny access to a field before initialization. Final fields are beautiful.

It's often hard to know which is which looking at the 22 arguments in a ctor call (e.g. they include literals). However, a cheap sweetener is the IDE-refactor tool introduce-local-variable. In contrast, setter serves as simple documentation, but some IDE are unable to update setter names when we rename a field.

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