Clean Code

Best practice Luigi De Russis

Clean Code

2 Measuring code quality

Clean Code 07/03/2013

The only valid measurement: WTFs/min
3

Good code Bad code

WTF,
WTF WTF this is shit!

CODE CODE
REVIEW WTF REVIEW WTF
WTF

Dude,
WTF

WTF


4 Goals


Code MUST be…
5

Readable Maintainable

Extendable Testable

6 How?


8 Meaningful names


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?


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?


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?


What we have done
12

Used intention flaggedCells rather
revealing names than list

Replaced magic cell[STATUS_VALUE]
numbers with constants rather than x[0]

Created an appropriate Cell cell rather than
abstract data type int[] cell


Another example…
13

class DtaRcrd102
{
private Date genymdhms;
private Date modymdhms;
private final String pszqint = “102”;
/* ... */
}

Use pronounceable and searchable names
(please!)


Another example…
14

class Customer
{
private Date generationTimeStamp;
private Date modificationTimeStamp;
private final String recordId = “102”;
/* ... */
}

Better?


15 Functions


Functions
16

Small

Do One Thing


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?


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.


Functions
19

Handle errors (and use exceptions)

Don’t Repeat Yourself
(avoid copy-and-paste code)


20 Comments


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())


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())


API Documentation

YES Explanation of intent
Clarification
Warning of consequences

Orphan comments

NO Obsolete comments
Noise comments
Code commented-out

23 Clean Code 07/03/2013

24 Formatting


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


Breaking Indentation
26

public class CommentWidget extends TextWidget {
public static final String REGEXP =
“^#[rn]*(?:(?:rn)|n|r)?”;
public CommentWidget(String text) { super(text); }
public String render() throws Exception { return “”; }
}

Eh?


Breaking Indentation
27

public class CommentWidget extends TextWidget
{
public static final String REGEXP =
“^#[rn]*(?:(?:rn)|n|r)?”;

public CommentWidget(String text)
{ Better?
super(text);
}

public String render() throws Exception
{
return “”;
}
}


28 Conventions


Conventions
29

Conventions enable common
understanding

Stick to the language-specific conventions

Respect team-level conventions
Still complying with the language-specific conventions…

References
30

 Robert C. Martin Series, “Clean Code - A Handbook
of Agile Software Craftsmanship”, Prentice Hall
 Geek and Poke,
http://geekandpoke.typepad.com/
 OSNews Comics, http://www.osnews.com/comics


License
31

 This work is licensed under the Creative Commons “Attribution-
NonCommercial-ShareAlike Unported (CC BY-NC-SA 3,0)” License.
 You are free:
 to Share - to copy, distribute and transmit the work
 to Remix - to adapt the work
 Under the following conditions:
 Attribution - You must attribute the work in the manner specified by the
author or licensor (but not in any way that suggests that they endorse
you or your use of the work).
 Noncommercial - You may not use this work for commercial purposes.
 Share Alike - If you alter, transform, or build upon this work, you may
distribute the resulting work only under the same or similar license to this
one.
 To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc-sa/3.0/

Clean Code

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie Clean Code

Ähnlich wie Clean Code (20)

Mehr von Luigi De Russis

Mehr von Luigi De Russis (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Clean Code