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Clean Code:A Quick Review

linkedin.com/in/elgeish

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Things Covered Here

1 About the Book

2 Why Clean Code?

3 Things We Liked

4 Things We Disliked

2

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 Coding for Machines

Quick Reminder

IN AX, DX

MOV [ES:DI], AX

INT 3

MOV AX, [DS:SI]

OUT DX, AX

3

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About the Book

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 It’s all about craftsmanshipA Handbook of Agile Software Craftsmanship

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• Amazon best seller in software testing

• Uncle Bob is also known for SOLID

• He also wrote The Clean Coder (2011)

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Why Clean Code?

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 Because we write code for humans, and not just machinesCode Is Speech:

7Source: xkcd.com/1421

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 “We are honest about the state of our code because code is never perfect”, and that’s – actually – desirable!

Code Is Never Perfect:

8Source: xkcd.com/844

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 “[Coding] stops as soon as minimally-accepted results are found” - Guillaume Ferrero (1894)

Principle of Least Effort:

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Source: xkcd.com/221

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 Seeking delayed gratification (clean code) => a more successful lifeThe Stanford Marshmallow Experiment:

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Acceptable result?

Demand excellence

Have a cookie!

No

Yes

Have two cookies!

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 The secret is dopamineA Neuroscientific Look at Meh Code

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• Coding is iterative• A failure causes low dopamine levels• Task completion => a spike in dopamine levels• Moving on to a new task => dopamine levels rise

“[Yet] newness is no virtue and oldness is no vice. Truth and beauty and goodness are not determined by when they exist.”

- Pastor John Piper

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Things We Liked

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 Can save your lifeCoding Standards

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• Consistent indentation style => fewer bugs • Reduce attention deficit (Thinking, Fast and Slow)• Pick them, stick to them, and automate if possible

“Code formatting is about communication,and communication is the professional

developer's first order of business.”

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 As if you’re naming a first-born childMeaningful Names

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• We spend disproportionately more time reading coding (than writing it)

• Use the shortest most expressive name that you can find easily

“[An entity's name] should tell you why it exists, what it does, and how it is used.”

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 Keep everything smallMinimalism

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• Files, classes, functions, etc. should be small• SRP: Do one thing; do it well; and do it only!

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 // Do you really need this comment?Comments

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• When Bugs Become Features: Norman Doors• Can’t test a comment (TODO vs. @Expiration)• Comments are spells of magic; they charm the

reader into thinking they must be truer than code

“The proper use of comments is to compensate for our failure to express

[ourselves] in code.”

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Things We Disliked

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 Sometimes renaming might introduce bugsMeaningful Names

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• Tangled code reviews might hide an issue• Binary serialization might use private field names;

renaming them may cause compatibility issues!

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 Not the cleanest code

 Uncle Bob showed the use of comments to explain intent in this example:

 public int compareTo(Object o) {  if (o instanceof WikiPagePath) {  WikiPagePath p = (WikiPagePath) o;  String compressedName = StringUtil.join(names, “”);  String compressedArgumentName = StringUtil.join(p.names, “”);  return compressedName.compareTo(compressedArgumentName);  }  return 1; // we are greater because we are the right type. }

Comments

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 How would you review his code?

 Unnecessary Objects: There are better ways to compare iterables without creating throwaway objects (and especially not strings that are expensive to create – see Item 5 in Effective Java).

 Variable Names: they’re not meaningful.

 Choice of Words: "we" is not a known reference in programming; "this" is though, and it would have been more apt here.

 Eliminate the Comment Altogether: Implement Comparable{T} instead, or skip the type check; compareTo should throw ClassCastException if the types are different. Comparing two objects of different types violates many contracts.

Comments

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 SRPFunctions

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• “Functions should either do something or answer something, but not both”

• Yet, the Command-Query pattern is sometimes pragmatic in concurrent programming:• test-and-set: writes to a memory location, and

returns the old value• compare-and-swap: compares the value x at a

given memory location to a given value y, and sets the former to a given new value z only if x is equal to y; the return value indicates whether or not the swap occurred

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 Missing sectionsFunctions

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• Generics• Overloading• Default Parameters• Scope (visibility)• Testability

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