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I have been assigned the task to refactor a Delphi unit. Wow. 10000 lines of code, no documentation, tons of copy and paste code.
THere are many methods made with copy and paste that could be refactored, anyway I am lost in all those lines, I have the interface section where I can "find my way", but in general what do yuo suggest for tackling this kind of task?
Thanks.
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The most common cause of refactoring problems is not in the code -- it's a lack of proper tools. Refactoring nearly always includes renaming variables and methods, changing method signatures, and moving things around. Trying to make all these changes by hand can easily lead to disaster.
General logic based on this: If points 1-5 are all true, don't refactor. If any of points 2, 3, or 5 are false for multiple reasons (for example, multiple bugs would be fixed or multiple features would be easier to implement), count them as false once for each reason they are false.
Refactoring is difficult because many, if not most, programmers do not know what the end result should be. They have really never seen well written code and have been taught since writing their first line of code that if it compiles and runs, that is enough.
The best time to consider refactoring is before adding any updates or new features to existing code. Going back and cleaning up the current code before adding in new programming will not only improve the quality of the product itself, it will make it easier for future developers to build on the original code.
I would also recommend bookmarking http://www.refactoring.com/catalog/ and http://www.industriallogic.com/xp/refactoring/catalog.html.
It also wouldn't hurt to get a copy of Clean Code: A Handbook of Agile Software Craftsmanship by Robert "Uncle Bob" Martin et al. It's easy to recognize bad code. It's much harder know when you're writing good code.
A word of caution: Focus on refactoring the code you need to work on. Its easy to start down the rabbit hole and wind up spending months refactoring code that wasn't immediately relevant to the task at hand.
And save your self some trouble. Don't try to "fix" code and refactor it at the same time. Refactor first, then fix bugs or add that new feature. Remember, refactoring is modifying without changing external behavior.
Resist the urge to attempt a complete rewrite. I learned the hard way that crappy code that meets the user's requirements is preferable to clean code that doesn't. Crappy code can always be incrementally improved until its something to be proud of.
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