Clean Code 2
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The document discusses clean code principles such as writing code for readability by other programmers, using meaningful names, following the DRY principle of not repeating yourself, and focusing on writing code that is maintainable and changeable. It provides examples of clean code versus less clean code and emphasizes that code is written primarily for human consumption by other programmers, not for computers. The document also discusses principles like the Single Responsibility Principle and the Boy Scout Rule of leaving the code cleaner than how you found it. It questions how to measure clean code and emphasizes the importance of writing tests for code and refactoring legacy code without tests.
![public List<int[]> getThem() {
List<int[]> list1 = new ArrayList<int[]>();
for (int[] x : theList)
if (x[0] == 4)
list1.add(x);
return list1;
}](https://image.slidesharecdn.com/cleancode-english-120523165920-phpapp01/85/Clean-Code-2-16-320.jpg)
![public List<int[]> getThem() {
List<int[]> list1 = new ArrayList<int[]>();
for (int[] cell : gameBoard)
if (cell[STATUS_VALUE] == FLAGGED)
list1.add(cell);
return list1;
}](https://image.slidesharecdn.com/cleancode-english-120523165920-phpapp01/85/Clean-Code-2-17-320.jpg)
![public List<int[]> getFlaggedCells() {
List<int[]> flaggedCells = new ArrayList<int[]>();
for (int[] cell : gameBoard)
if (cell[STATUS_VALUE] == FLAGGED)
flaggedCells.add(cell);
return flaggedCells;
}](https://image.slidesharecdn.com/cleancode-english-120523165920-phpapp01/85/Clean-Code-2-18-320.jpg)
Clean Code 2
- 3. Clean Code what, why, how
- 5. Disclaimer Correlation between Clean code and success?
- 6. How is it even possible for code to be this bad?
- 7. Exhibits • Hudson class is 3900+ LOC • Hudson class is untestable Singleton • Constructor calls a method that gets the singleton instance and calls a method on the instance. • Hudson extends Node, but Node calls methods defined in Hudson
- 8. WTF! So why care – Jenkins is great?
- 10. ”Smart” vs Professional • Smart • Professional ● Great coding skills ● Readable code ● Writes advanced code ● Maintainable code ● String r; // lowercase url ● 'Clarity is king' ● String lowerCaseUrl OfCurrentPage; http://www.slideshare.net/JandV/clean-code-summary
- 11. What is Clean Code?
- 12. int d; // elapsed time in days
- 13. int d; // elapsed time in days int elapsedTimeInDays;
- 14. int d; // elapsed time in days int elapsedTimeInDays; int daysSinceCreation;
- 15. int d; // elapsed time in days int elapsedTimeInDays; int daysSinceCreation; int fileAgeInDays;
- 16. public List<int[]> getThem() { List<int[]> list1 = new ArrayList<int[]>(); for (int[] x : theList) if (x[0] == 4) list1.add(x); return list1; }
- 17. public List<int[]> getThem() { List<int[]> list1 = new ArrayList<int[]>(); for (int[] cell : gameBoard) if (cell[STATUS_VALUE] == FLAGGED) list1.add(cell); return list1; }
- 18. public List<int[]> getFlaggedCells() { List<int[]> flaggedCells = new ArrayList<int[]>(); for (int[] cell : gameBoard) if (cell[STATUS_VALUE] == FLAGGED) flaggedCells.add(cell); return flaggedCells; }
- 19. public List<Cell> getFlaggedCells() { List<Cell> flaggedCells = new ArrayList<Cell>(); for (Cell cell : gameBoard) if (cell.isFlagged()) flaggedCells.add(cell); return flaggedCells; }
- 20. Clean code always looks like it was written by someone who cares
- 21. Clean code always looks like it was wrtten by somone who craes
- 23. Agile Manifesto Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan
- 25. Readable?
- 26. ~ 90% of your time is reading What if you'd ddouble write-time and thereby cut read-time by half?
- 27. public class Part { private String m_dsc; // The textual description void setName(String name) { m_dsc = name; } } public class Part { private String description; void setDescription(String description) { this.description = description; } }
- 29. Code is written for humans!
- 30. Why? Who's the main recipient of the code we write – a computer, an end user or a programmer? The primary user of source code is a programmer, perhaps ● your Customer ● your Colleague ● You
- 31. How should I write code?
- 32. DRY - Don't Repeat Yourself YAGNI - You Ain't Gonna Need It
- 33. small
- 34. Meaningful Names • Intention-Revealing • JobQueue • Pronounceable • Words from the domain • Avoid Encoding • Comments • Classes • Formatting! • Methods
- 35. Law of Demeter More formally, the Law of Demeter for functions requires that a method M of an object O may only invoke the methods of the following kinds of objects: 1. O itself 2. M's parameters 3. any objects created/instantiated within M 4. O's direct component objects 5. a variable, accessible by O, in the scope of M
- 36. Dog's Legs public class CareTaker { private Dog dog; ... public void walkTheDog(){ dog.walk(); dog.stop(); // tree or grass etc dog.doYourThing(); ... } }
- 37. Dog's Legs public class CareTaker { private Dog dog; ... public void walkTheDog(){ for (Leg leg : dog.getLegs()) leg.move(); for (Leg leg : dog.getLegs()) leg.stopMoving(); dog.brain.urinationCenter.releaseUrge(); ... } }
- 38. Don't talk to strangers http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/paper-boy/
- 39. Law of Demeter public class PaperBoy { private Wallet myWallet; ... public void chargeCustomer(Customer customer) { Wallet wallet = customer.getWallet(); Collection<Bill> bills = wallet.getBills(); Collection<Bill> payment = extract(5, bills); myWallet.add(payment); // or bills? } }
- 40. Law of Demeter public class PaperBoy { private Wallet myWallet; ... public void chargeCustomer(Customer customer) { Collection<Bill> payment = customer.getPayment(5); myWallet.add(payment); } }
- 41. Single Responsibility 1 small
- 43. Boy Scout Rule Leave the campground cleaner than you found it.
- 44. Hur mäter man Clean Code? Eller kodkvalitet?
- 45. Can you measure Clean Code? Or code quality?
- 46. WTFs / minute The only valid measurement of code quality
- 47. Summary Source code vs machine code Write with the audience in minde Smart vs Professional Code quality and retrospectives Code Review (wtf!) vs pair programming
- 48. Legacy Code Code with no tests
- 49. What about the code that's already in my backpack? • Get the old man on track – make the code testable (and tested) • Fix bugs brought out in daylight by the tests • ”Make it right”
- 50. What about the code that's already in my backpack? • Get the old man on track – make the code testable (and tested) • Fix bugs brought out in daylight by the tests • ”Make it right” – refactor!
- 51. Code without tests ... • is legacy code • is not refactored • unlikely to be changed by someone other than the person who wrote it (the past few days) • is heavy load/back pack