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How to Find the Stinky Parts of Your Code [Part XVIII]

by Maximiliano ContieriMay 4th, 2022

Too Long; Didn't Read

It smells because there are likely many instances where it could be edited or improved. Most of these smells are just hints of something that might be wrong.

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featured image - How to Find the Stinky Parts of Your Code [Part XVIII]

Infinite code, smells!

It smells because there are likely many instances where it could be edited or improved.

Most of these smells are just hints of something that might be wrong. They are not required fixed per se… ( You should look into it though.)

Previous Code Smells

Let's continue...

Code Smell 86 - Mutable Const Arrays

Const declares something to be constant. Can it mutate?

TL;DR: Don't rely on languages cheating about directives.

Problems

Unexpected side effects
Accidental complexity

Solutions

Use better languages
Use spread operator

Sample Code

Wrong

const array = [1, 2];

array.push(3)

//array => [1, 2, 3]
//Wasn't it constant ?
//constant != immutable ?

Right

const array = [1, 2];

const newArray = [...array,3 ]

//array => [1, 2] Didn't mutate
//newArray = [1, 2, 3]

Detection

Since this is a "language feature", we can explicitly forbid it.

Conclusion

We should always favour immutability on our designs and take extra care with side effects.

More Info

The evil power of mutants

Credits

Photo by Zorik D on Unsplash

Twitter

Correctness is clearly the prime quality. If a system does not do what it is supposed to do, then everything else about it matters little.

Bertrand Meyer

Code Smell 87 - Inconsistent Parameters Sorting

Be consistent with the parameters you use. Code is prose.

TL;DR: Don't confuse you readers. Keep the order.

Problems

Readability
Consistency

Solutions

Refactor and change parameters order.
Use named parameters

Sample Code

Wrong

function giveFirstDoseOfVaccine(person, vaccine) {
  //
}

function giveSecondDoseOfVaccine(vaccine, person) {
  //
}


giveFirstDoseOfVaccine(jane, pfizer);
giveSecondDoseOfVaccine(jane, pfizer);  //Unnoticed mistake

Right

function giveFirstDoseOfVaccine(person, vaccine) {
  //
}

function giveSecondDoseOfVaccine(person, vaccine) {
  //
}


giveFirstDoseOfVaccine(jane, pfizer);
giveSecondDoseOfVaccine(jane, pfizer);  //Jane is immunized

Detection

Some very smart linters may be able to compare arguments and hint for possible mistakes.

Conclusion

This is a very simple smell.

Readability is very important to avoid mistakes.

Relations

Code Smell 10 - Too Many Arguments

Credits

Photo by Lance Grandahl on Unsplash

Twitter

Computers are good at following instructions, but not at reading your mind.

Donald Knuth

Code Smell 88 - Lazy Initialization

Yet another premature optimization pattern

TL;DR: Do not use lazy initialization. Use an object provider instead.

Problems

Surprising Side Effects
Premature Optimization
Fail Fast Violation
Implementative Coupling
The Least Surprise Principle Violation
Null Usage
Mutability
Transactional and Multi-threaded applications problems
Debugging Problems

Solutions

Inject Responsibilities with First Class Objects

Sample Code

Wrong

class Employee
  def emails
    @emails ||= []
  end
  
  def voice_mails
    @voice_mails ||= []
  end
end

Right

class Employee
  attr_reader :emails, :voice_mails

  def initialize
    @emails = []
    @voice_mails = []
  end
end
#We can also inject a design pattern to externally deal
#with voice_mails so we can mock it in our tests

Detection

Lazy initialization is a common pattern when used checking for a non-initialized variable.

It should be straightforward to detect them.

Conclusion

Singletons are another antipattern often combined with lazy initialization.

We must avoid premature optimizations. If we have real performance problems we should use a Proxy, Facade or more independent solution.

Relations

Code Smell 32 - Singletons

Code Smell 12 - Null

More Info

Credits

Photo by Sam Solomon on Unsplash

We have to stop optimizing for programmers and start optimizing for users.

Jeff Atwood

Code Smell 89 - Math Feature Envy

One class calculating formulas for another class.

TL;DR: Leave the formulas to the objects gathering the information.

Problems

Declaratively
Low reuse
Real-world concept missing
Encapsulation

Solutions

Move the math formula to the class
Search for real-world abstractions

Sample Code

Wrong

function area(rectangle) { 
  return rectange.width * rectangle.height;
  //Notice we are sending consecutive messages to
  //the same object and doing calculations
}

Right

class Rectangle {
    constructor(width, height, color) { 
         this.height = height;
         this.width = width;
    }
 
    area() {
        return this.width * this.height;
    }
}

Detection

Since many cascading messages are sending to the same object, we can detect a pattern.

Conclusion

This is a very basic smell. If we are manipulating another object characteristics, we should let it do it the maths for us.

Relations

Code Smell 63 - Feature Envy

More Info

The one and only one software principle

Credits

Photo by Michal Matlon on Unsplash

Computer science is not about machines, in the same way that astronomy is not about telescopes. There is an essential unity of mathematics and computer science.

Michael R. Fellows

Code Smell 90 - Implementative Callback Events

When creating events, we should decouple the trigger from the action.

TL;DR: Name your functions acording to what happened.

Problems

Observer Pattern violation
Coupling

Solutions

Name the events after "what happened", not "what you should do".

Sample Code

Wrong

const Item = ({name, handlePageChange)} =>
  <li onClick={handlePageChange}>
    {name}
  </li>

//handlePageChange is coupled to what you decide to do
//instead of what really happened
//
//We cannot reuse this kind of callbacks

Right

const Item = ({name, onItemSelected)} =>
  <li onClick={onItemSelected}>
    {name}
  </li>

//onItemSelected will be called just when a item was selected. KISS
//Parent can decide what to do (or do nothing)
//We defer the decision