Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Software Craftsmanship - 2

7,401 views

Published on

2nd Meeting of the Software Craftsmanship in Israel Group

Published in: Technology
  • Be the first to comment

  • Be the first to like this

Software Craftsmanship - 2

  1. 1. Software Craftsmanship<br />Meeting #2<br />http://www.flickr.com/photos/renfield/17375998/in/set-388814/<br />
  2. 2. Agenda<br />Bad Code / Good Code<br />Code Smells<br />Tools<br />Hands On<br />Code Dojo<br />Identifying Smells *<br />
  3. 3. WTF<br /> publicstaticbooleanisValidNumber(Integer number) {<br />methodName = "isValidNumber";<br /> Logger logger = LoggingHelper.getLogger(LOGGER);<br />logger.entering (CLASS, methodName);<br /> // parse this number. If you get an NFE, then its <br /> // not valid, return false<br />try {<br />Integer.parseInt(number.toString());<br /> } catch(Exception ex) {<br />logger.fine(methodName + " returns false");<br />logger.fine("Number Format Exception when parsing");<br /> return false; <br /> }<br />logger.fine(methodName + " returns true");<br />logger.exiting(CLASS, methodName); <br /> return true; <br /> }<br />Logging Entry<br />WTF?<br />Logging Exit<br />
  4. 4. WTF<br />while(true)<br />{<br />if(mainType == 7)<br /> {<br />subType = 4;<br />break;<br /> }<br />if(mainType == 9)<br /> {<br />subType = 6;<br />break;<br /> }<br />if(mainType == 11)<br /> {<br />subType = 9;<br />break;<br /> }<br />break;<br />}<br />/*<br />=============<br />checkSize<br />Make sure the image is a power of 2.<br />=============<br />*/<br />intcheckSize(int x) {<br />if (x == 2 || x == 4 || x == 8 || x == 16 || x == 32 || x == 64 || x == 128 || x == 256 || x == 512)<br />return 1;<br />else<br />return 0;<br />}<br />WTF?<br />WTF?<br />
  5. 5. WTF<br />DirectoryInfo dir = new DirectoryInfo(pathToDelete);<br />// subDirs<br />DirectoryInfo[] subDirs = dir.GetDirectories();<br />foreach(DirectoryInfosubDirinsubDirs)<br />{<br /> // subSubDirs<br />DirectoryInfo[] subSubDirs = subDir.GetDirectories();<br />foreach(DirectoryInfosubSubDir in subSubDirs)<br /> {<br /> // subSubSubDirs<br />DirectoryInfo[] subSubSubDirs = subSubDir.GetDirectories();<br />foreach(DirectoryInfosubSubSubDirinsubSubSubDirs)<br /> {<br /> // subSubSubSubDirs<br />DirectoryInfo[] subSubSubSubDirs = subSubSubDir.GetDirectories();<br />foreach(DirectoryInfosubSubSubSubDirinsubSubSubSubDirs)<br /> {<br /> // ********************************************<br /> // should be enough; if not, I can add more here<br /> // ********************************************<br />WTF?<br />WTF?<br />
  6. 6. Code Smell<br />http://www.flickr.com/photos/brian-fitzgerald/3334353375/<br />http://www.flickr.com/photos/yomi955/1192827822/<br />Code Smell - In computer programming, code smell is any symptom in the source code of a program that possibly indicates a deeper problem<br />http://en.wikipedia.org/wiki/Code_smell<br />
  7. 7. Code Smells<br />Duplicated Code<br />Same code structure in more than one place:<br />Same expression in two methods of the same class<br />Same expression in two sibling subclasses<br />Same expression in two unrelated classes<br />
  8. 8. Code Smells<br />
  9. 9. Demo<br />Clone Detector<br />
  10. 10. Code Smells<br />Long Method<br />A good technique is to look for comments. They often signal a semantic distance between the intension of the code and the implementation of the code<br />The net effect is that you should be much more aggressive about decomposing methods<br />The desired length should be 5-8 lines<br />
  11. 11. Code Smells<br />
  12. 12. Demo<br />Comments, please!<br />
  13. 13. Code Smells<br />Large Class<br />Many instance variables indicates that a class tries to do too much<br />Many instance variables can indicate a duplicate code<br />Too much code is prime breeding ground for duplicated code, chaos, and death <br />
  14. 14. Code Smells<br />
  15. 15. Demo<br />How Many Lines?<br />
  16. 16. Code Smells<br />Long Parameter List<br />In the past we passed in as parameters everything needed by a routine. With objects it’s not required; instead enough parameters passed in to the method in order to allow it to get everything rest it needs<br />Long parameter lists are hard to understand<br />Long parameter lists inconsistent and difficult to use<br />Long parameter lists are forever changed as more data is required <br />
  17. 17. Code Smells<br />
  18. 18. Code Smells<br />Long Parameter List<br />Avoid output parameters (ref, out)<br />Avoid boolean arguments<br />Avoid more than 3 arguments<br />2 is preferable<br />1 is better<br />0 is the best<br />Introduce Parameter Object<br />Refactoring Step<br />Separate Query From Modifier<br />Refactoring Step<br />One return value.<br />
  19. 19. Demo<br />To Query or To Modify?<br />
  20. 20. Code Smells<br />Switch Statements<br />The problem with switch statements is essentially that of duplication i.e. the same switch statement scattered about a program in different places<br />Most times you see a switch statement you should consider polymorphism <br />
  21. 21. Code Smells<br />
  22. 22. Demo<br />How to Process Request<br />
  23. 23. Code Smells<br />Speculative Generality<br />A class that exists to support some future and imaginary feature.<br />“We might need this one day …”<br />If you really do need it later, you can add it easily using Refactoring.<br />It doesn’t mean you don’t need to anticipate requirements and features.<br />
  24. 24. Code Smells<br />Comments<br />When you feel the need to write a comment, first try to refactor the code so that any comment becomes superfluous<br />
  25. 25. Code Smells<br />Feature Envoy<br />A method that seems more interested in a class other than the one it actually is in<br />Data and the behavior that references that data usually change together, but there are exceptions:<br />Visitor<br />Strategy<br />
  26. 26. Code Smells<br />
  27. 27. Code Smells<br />Message Chains<br />A client asks one object for another object, which the client then asks for yet another object, which the client then asks for yet another another object, and so on<br />Can be seen as a long line of GetThis() methods, or as a sequence of temps<br />Any change to the intermediate relationships causes the client to have to change<br />Account.Owner.OwnerDetails.Address.Zip<br />
  28. 28. Hands On<br />Dojo<br />Code Smells<br />http://www.flickr.com/photos/renfield/351556388/in/photostream/<br />
  29. 29. Roman Numbers: ToString()<br />0<br />Nulla<br />Numerals<br />
  30. 30. Roman Numbers: ToString()<br />I<br />The values of each roman letter can be additive<br />II<br />The larger numerals must be placed to the left of the <br />smaller numerals<br />III<br />At the fourth iteration, a subtractive principle may be<br />employed, with the base placed before the higher base:<br />IIII or IV <br />The subtracted digit must be at least one tenth of the<br />value of the larger numeral. Therefore: 99 isn’t IC but<br />rather XCIX<br />
  31. 31. 2nd Meeting of the Software Craftsmanship Group<br />http://www.flickr.com/photos/psd/2086641/<br />

×