Delphi what is refactoring

In this case, we have a method or function that has some code that we would like to reuse. The principle says that this code needs to be extracted and placed externally onto another function and then add the call where the previous code was. This technique is very simple and very easy to embrace for code reusability. As you can see this is a very simple example where I request a web page and then I do some parsing to get the list of urls that are part of the html document.

Let's see how to refactor it to make it more reusable. Notice that I've extracted the parsing functionality and I've created a parseHTML function that gets the response and parses it and returns the list of urls. Now I can reuse my parsing functionality should I have any other page where this functionality is required.

No-brainer here. This one is a bit different and it relates to the outer code as a reusable code. Go Up to Refactoring Applications Index. Refactoring is a technique you can use to restructure and modify your existing code in such a way that the intended behavior of your code stays the same. Refactoring allows you to streamline, simplify, and improve both performance and readability of your application code. Each refactoring operation acts upon one specific type of identifiers.

By performing a number of successive refactorings, you build up a large transformation of the code structure, and yet, because each refactoring is limited to a single type of object or operation, the margin of error is small.

You can always back out of a particular refactoring, if you find that it gives you an unexpected result. Each refactoring operation has its own set of constraints.

You can even assist here with unit test, by writing tests that succeed because of the bug. They can be removed, or better re-written when they start to fail because the bug has been fixed. This answer is a mine to explore. I personally expereinced on myself the terrible results of refactoring and fixing code. Also refactoring and adding features. Anyway as you say "real refactoring" shouldn't add features.

I will buy both books, I aready have them in my amazon wish list since 2 years It is time to buy! I recommend ModelMaker CodeExplorer.

Also, Splash is right to recommend you write unit tests, before refactoring, so that you can test that you didn't break anything. Working Effectively with Legacy Code is worth the read - I'm rereading it at the moment.

It might not be possible to write unit tests initially too many dependencies for instance , so your first task might be to refactor bits of the code to remove some of these dependencies to a point where testing is feasible.

At which point you can write as many tests as needed for you to confidently make changes in the code. Add a comment. Tests Reduce Bugs in Existing Features. Tests Are Good Documentation. Tests Reduce the Cost of Change. Tests Improve Design. Tests Allow Refactoring.

Can you please redirect me to a link to test units that interact with database data. Unit tests are clear to me, but only for business class units. One pitfall you will have to look out for when creating unit tests for existing code, is that it is very easy to lull yourself into a false sense of security.

Succeeding tests may just nog stretch the code enough. And if you write tests that force an error condition to check that the error is raised, check for the specific error.

Otherwise the test may succeed because an error was detected, but it may not be the error you were looking for I've faced similar situations. My condolences to you! You might also think about creating a good test suite that runs on the current code. RobertFrank RobertFrank 7, 10 10 gold badges 48 48 silver badges 94 94 bronze badges. Yes, you are right. Refactoring wihtout understanding the code is impossible, anyway it takes lot of time for records, but probalby dome parts can be skipped.

It is definitely possible to refactor code with out initially understanding it - I have done so a number of times, you of course have to be very mechanical in doing it so as not to change the behaviour.

Be prepared to play around with the code, and throw away many changes - as you begin to understand the code better you will find clear places to clean the code up. I would recommend reading Martin Fowlers Refactoring book first however. Refactoring can be an excellent way of getting to understand unfamiliar Legacy code and improving on it. Wim ten Brink Wim ten Brink 25k 19 19 gold badges 75 75 silver badges bronze badges. These are excellent low level points. My personal experience has been that without unit tests, such a complete split-up of units without breaking everything, is next to impossible.

Harriv Harriv 5, 6 6 gold badges 42 42 silver badges 75 75 bronze badges. Roise Roise 6 6 silver badges 22 22 bronze badges. Sadly, you may get a whole book of overview from such tools thrown on such files, so you need again tools to read the output.

Use a tool like Doxygen to help you map the code. Help on that is here.