3. Bjarne Stroustrup, inventor of C++
and author of The C++ Programming
Language
I like my code to be elegant and efficient. The logic should be
straightforward to make it hard for bugs to hide, the
dependencies minimal to ease maintenance, error handling
complete according to an articulated strategy, and per-
formance close to optimal so as not to tempt people to make
the code messy with unprinci-pled optimizations. Clean code
does one thing well.
4. “Big” Dave Thomas, founder
of OTI, godfather of the
Eclipse strategy
Clean code can be read, and enhanced by a developer other
than its original author. It has unit and acceptance tests. It has
meaningful names. It provides one way rather than many ways
for doing one thing. It has minimal depen dencies, which are
explicitly defined, and pro- vides a clear and minimal API. Code
should be literate since depending on the language, not all
necessary information can be expressed clearly in code alone.
5. Michael Feathers, author of Working
Effectively with Legacy Code
I could list all of the qualities that I notice in clean code, but
there is one overarching quality that leads to all of them.
Clean code always looks like it was written by someone who
cares. There is nothing obvious that you can do to make it
better. All of those things were thought about by the code’s
author, and if you try to imagine improvements, you’re led
back to where you are, sitting in appreciation of the code
someone left for you—code left by some one who cares
deeply about the craft.
6. My personal View
The code considered to be clean will need these:
Well written test (Unit test) for every public methods.
A class should be small and does one thing only
A method should be small enough( not longer then 20 lines)
A method should does only one thing and does it well
After all, I should able to hand over my code to other, and they should
able to carry on the work.
8. Meaningfull Names
Use Intention-Revealing Names:
Intention-
It should tell you why it exists, what it does, and how it is
used.
int d; // elapsed time in days
OR
int elapsedTimeInDays;
int daysSinceCreation;
int daysSinceModification;
int fileAgeInDays;
9. Avoid Disinformation
avoid words whose entrenched meanings vary from
our intended meaning.
Eg. grouping of accounts -> var accountList
10. Use Pronounceable Names
class DtaRcrd102 {
private Date genymdhms;
private Date modymdhms;
private final String pszqint = "102";
/* ... */
};
To
class Customer {
private Date generationTimestamp;
private Date modificationTimestamp;;
private final String recordId = "102";
/* ... */
};
11. Avoid Encodings
Hungarian Notation
PhoneNumber phoneString;
// name not changed when type changed!
Member Prefixes
public class Part {
private String m_dsc; // The textual
description
void setName(String name) {
m_dsc = name;
}
} To
public class Part {
String description;
void setDescription(String description) {
this.description = description;
}
}
12. Avoid Mental Mapping
Readers shouldn’t have to mentally translate your
names into other names they already know.
This problem generally arises from a choice to use
neither problem domain terms nor solution domain
terms.
var r; //url
var fn; //first name
15. Pick One Word per Concept
Pick one word for one abstract concept and stick with it
Eg.
Fetch(), retrieve(), get() as equivalent
methods of different classes.
controller and a manager and a driver in the same code base.
16. Don’t Pun
Avoid using the same word for two purposes
Eg.
add(firstItem, secondItem), concatinat two items.
add(newItem), append to existing item
17. Use Solution Domain Names
Do not afraid of using computer science team like:
Name of patters
Algorithm
• getMinWidthComposite()
•AccountVisitor
18. Add Meaningful Context
enclosing them in well-named classes, functions, or
namespaces
private void thereIsOneLetter() {
number = "1";
verb = "is";
pluralModifier = "";
}
19. Function
Small, should be hardly every 20 lines long
Does one thing, it should does one thing, does it well,
and does it only.
20. Function: One Level of Abstraction per
Function
gtk.Button.prototype.setImage = function(image){
this._widget2 = image;
this.resize(this._minWidth, this._minHeight);
this._widget2._domObj.style.display = "";
this._imageDom.appendChild(this._widget2._domObj);
};
To
gtk.Button.prototype.setImage = function(image){
this._widget2 = image;
this.resize(this._minWidth, this._minHeight);
this.hide(this._widget2);
this._appendImage(this._widget2._domObj);
};
gtk.Button.prototype.hideWidget = function(widget){
widget._domObj.style.display = "";
};
gtk.Button.prototype.appendImage = function(){
this._imageDom.appendChild(this._widget2._domObj);
};
21. Function Arguments
What is the best number of arugments passed in:
Zero (niladic)
Two (dyadic)
Three (polyadic)
More then this is evil
Reasons not to have many arguments:
For public methods, user fine it hard to use the method.
For private method, it should able to access the class
properties, why have to pass in.
22. Function Arguments
Flag Arguments: Passing a boolean into a function is a truly
terrible practice
render(true)
OR
renderForSuite() and renderForSingleTest()
23. Function Arguments
Argument Objects: more than two or three arguments, they
ought to be wrapped into a class of their own.
Circle makeCircle(double x, double y,
double radius);
OR
Circle(circleProperties);
24. Don’t repeat yourself
If you see the same code structure more than one
place, then extract the method and invoke the code
from both places
25. Switch Statement
How to make switch statement does one thing?
public Money calculatePay(Employee e)
throws InvalidEmployeeType {
switch (e.type) {
case COMMISSIONED:
return calculateCommissionedPay(e);
case HOURLY:
return calculateHourlyPay(e);
case SALARIED:
return calculateSalariedPay(e);
default:
throw new InvalidEmployeeType(e.type);
}
}
26. Comment
Comments Do Not Make Up for Bad Code:
“Ooh, I’d better comment that!” No! You’d better
clean it!”
// Check to see if the employee is eligible for full
benefits
if ((employee.flags & HOURLY_FLAG) && (employee.age >
65))
OR
if (employee.isEligibleForFullBenefits())
28. Comment
Legal Comments
// Copyright (C) 2003,2004,2005 by Object Mentor, Inc. All rights reserved.
// Released under terms of the GNU General Public License version 2 or later.
Informative Comments
// Returns an instance of the Responder being tested.
protected abstract Responder responderInstance();
OR
protected abstract Responder getResponderInstance();
29. Warning of Consequences
Warning of Consequences
// Don't run unless you
// have some time to kill.
public void _testWithReallyBigFile()
{
writeLinesToFile(10000000);
response.setBody(testFile);
response.readyToSend(this);
String responseString = output.toString();
assertSubString("Content-Length: 1000000000", responseString);
assertTrue(bytesSent > 1000000000);
}
30. TODO Comments
Leave TODO comment
//TODO-MdM these are not needed
// We expect this to go away when we do the checkout model
protected VersionInfo makeVersion() throws Exception
{
return null;
}
32. Redundant Comments
The comment that takes longer to read than the code
itself
// Utility method that returns when this.closed is true. Throws an exception
// if the timeout is reached.
public synchronized void waitForClose(final long timeoutMillis) throws Exception
{
if(!closed)
{
wait(timeoutMillis);
if(!closed)
throw new Exception("MockResponseSender could not be
closed");
}
}
33. Noise Comments
Sometimes you see comments that are nothing but noise.
They restate the obvious and provide no new information.
/**
* Returns the day of the month.
*
* @return the day of the month.
*/
public int getDayOfMonth() {
return dayOfMonth;
}
34. Don’t Use a Comment When You Can Use a
Function or a Variable
// does the module from the global list <mod> depend on the
// subsystem we are part of?
if (smodule.getDependSubsystems().contains(subSysMod.getSubSystem()))
OR
ArrayList moduleDependees = smodule.getDependSubsystems();
String ourSubSystem = subSysMod.getSubSystem();
if (moduleDependees.contains(ourSubSystem))
35. Position Markers
Mark a particular position in a source file
// Actions //////////////////////////////////
36. Class Names
Classes and objects should have noun or noun phrase
names like Customer, WikiPage, Account, and
AddressParser.
37. Reference
Clean Code: a hand book of agile software
craftmanship by Robert C. Martin
Refactoring, Improving the design of existing
code by Martin Fowler
