Clean Code

Best practice Luigi De Russis

Measuring code quality

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The only valid measurement: WTFs/min

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Good code Bad code

CODE REVIEW

CODE REVIEW

WTF

WTF

WTF

WTF

WTF

Dude, WTF

WTF, this is shit!

WTF

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Goals

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Code MUST be…

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Readable Maintainable

Extendable

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Testable

How?

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Meaningful names

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Clean Code

An example…

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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?

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An example…

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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?

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An example…

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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?

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What we have done

cell[STATUS_VALUE]

rather than x[0]

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Used intention

revealing names

Replaced magic

numbers with constants

flaggedCells rather

than list

Created an appropriate

abstract data type

Cell cell rather than int[] cell

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Another example…

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class DtaRcrd102

{

private Date genymdhms;

private Date modymdhms;

private final String pszqint = “102”;

/* ... */

}

Use pronounceable and searchable names

(please!)

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Another example…

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class Customer

{

private Date generationTimeStamp;

private Date modificationTimeStamp;

private final String recordId = “102”;

/* ... */

}

Better?

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Functions

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Clean Code

Functions

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Small

Do One Thing

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Do One Thing

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?

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Do One Thing

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.

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Functions

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Handle errors (and use exceptions)

Don’t Repeat Yourself

(avoid copy-and-paste code)

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Comments

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Clean Code

Explain yourself in the code

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())

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Explain yourself in the code

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())

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NO Orphan comments

Obsolete comments

Noise comments

Code commented-out

YES API Documentation

Explanation of intent

Clarification

Warning of consequences

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Formatting

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Clean Code

Formatting

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Communication is the purpose of formatting

Vertical openness between concepts

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Each blank line is a visual cue that identifies a new and separate concept

Breaking Indentation

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?

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Breaking Indentation

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 “”;

}

}

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Better?

Conventions

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Clean Code

Conventions

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Stick to the language-specific conventions

Respect team-level conventions

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Still complying with the language-specific conventions…

Conventions enable common understanding

References

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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

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