Best practice. Luigi De Russis. Clean Code

Transcription

1 Best practice Luigi De Russis

2 2 Measuring code quality

3 The only valid measurement: WTFs/min 3 Good code Bad code WTF WTF WTF, this is shit! CODE REVIEW WTF WTF CODE REVIEW WTF Dude, WTF WTF

4 4 Goals

5 Code MUST be 5 Readable Maintainable Extendable Testable

6 6 How?

7 7

8 8 Meaningful names

9 An example 9 public List<int[]> getthem() { List<int[]> list = new ArrayList<int[]>(); for (int[] x : thelist) if (x[0] == 4) list.add(x); return list; } What does this code do?

10 An example 10 public List<int[]> getflaggedcells() { List<int[]> flaggedcells = new ArrayList<int[]>(); for (int[] cell : gameboard) if (cell[status_value] == FLAGGED) flaggedcell.add(cell); return flaggedcells; } Better?

11 An example 11 public List<Cell> getflaggedcells() { List<Cell> flaggedcells = new ArrayList<Cell>(); for (Cell cell : gameboard) if (cell.isflagged()) flaggedcell.add(cell); return flaggedcells; } What about this?

12 What we have done 12 Used intention revealing names flaggedcells rather than list Replaced magic numbers with constants cell[status_value] rather than x[0] Created an appropriate abstract data type Cell cell rather than int[] cell

13 Another example 13 class DtaRcrd102 { private Date genymdhms; private Date modymdhms; private final String pszqint = 102 ; /*... */ } Use pronounceable and searchable names (please!)

14 Another example 14 class Customer { private Date generationtimestamp; private Date modificationtimestamp; private final String recordid = 102 ; /*... */ } Better?

15 15 Functions

16 Functions 16 Small Do One Thing

17 Do One Thing 17 public bool isedible() { if(this.expirationdate > Date.Now && this.approvedforconsumption == true && this.inspectorid!= null) { return true; else return false; } How many things is the function doing?

18 Do One Thing 18 public bool isedible() { } return isfresh() && isapproved() && isinspected(); Now the function is doing one thing! A change in the specification turns into a single change in the code.

19 Functions 19 Handle errors (and use exceptions) Don t Repeat Yourself (avoid copy-and-paste code)

20 20 Comments

21 Explain yourself in the code 21 Which one is cleaner? //check to see if the employee is eligible for full benefits if((employee.flags & HOURLY_FLAG) && (employee.age > 65)) if(employee.iseligibleforfullbenefits())

22 Explain yourself in the code 22 Which one is cleaner? //check to see if the employee is eligible for full benefits if((employee.flags & HOURLY_FLAG) && (employee.age > 65)) if(employee.iseligibleforfullbenefits())

23 API Documentation YES Explanation of intent Clarification Warning of consequences Orphan comments NO Obsolete comments Noise comments Code commented-out 23

24 24 Formatting

25 Formatting 25 Communication is the purpose of formatting Vertical openness between concepts Each blank line is a visual cue that identifies a new and separate concept

26 Breaking Indentation 26 public class CommentWidget extends TextWidget { public static final String REGEXP = ^#[\r\n]*(?:(?:\r\n) \n \r)? ; public CommentWidget(String text) { super(text); } public String render() throws Exception { return ; } } Eh?

27 Breaking Indentation 27 public class CommentWidget extends TextWidget { public static final String REGEXP = ^#[\r\n]*(?:(?:\r\n) \n \r)? ; public CommentWidget(String text) { super(text); } Better? } public String render() throws Exception { return ; }

28 28 Conventions

29 Conventions 29 Conventions enable common understanding Stick to the language-specific conventions Respect team-level conventions Still complying with the language-specific conventions

30 References 30 Robert C. Martin Series, - A Handbook of Agile Software Craftsmanship, Prentice Hall Geek and Poke, OSNews Comics,

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