Maxi Contieri

Posted on Dec 15, 2021 • Originally published at maximilianocontieri.com

Code Smell 110 - Switches With Defaults

#oop #cleancode #codesmells #tutorial

Default means 'everything we don't know yet'. We cannot foresee the future.

TL;DR: Don't add a default clause to your cases. Change it for an exception. Be Explicit.

Problems

Coupling
Fail Fast principle violation
Open closed principle violation

Solutions

Replace if and cases with polymorphism
Change Default code to an Exception

Context

When using cases, we usually add a default case so it doesn't fail.

Failing is always better than taking decisions without evidence.

Since case and switches are also an smell, we can avoid them.

Sample Code

Wrong

switch (value) {
  case value1:
    //if value1 matches the following will be executed..
    doSomething();
    break;
  case value2:
    //if value2 matches the following will be executed..
    doSomethingElse();
    break;
  default:
    //if value does not presently match the above values
    //or future values
    //the following will be executed
    doSomethingSpecial();
    break;
}

Right

switch (value) {
  case value1:
    //if value1 matches the following will be executed..
    doSomething();
    break;
  case value2:
    //if value2 matches the following will be executed..
    doSomethingElse();
    break;
  case value3:
  case value4:
    //We currently know these options exist
    doSomethingSpecial();
    break;
  default:
    //if value does not match the above values we need to take a decision
    throw new Exception('Unexpected case ' + value + ' we need to consider it');
    break;
}

Detection

[X] Semi Automatic

We can tell our linters to warn us on default uses unless there's an exception.

Conclusion

Writing robust code doesn't mean we need to take decisions without evidence.

Relations

Code Smell 36 - Switch/case/elseif/else/if statements

Maxi Contieri ・ Nov 28 '20

#oop #webdev #tutorial #codenewbie

More Info

Fail Fast

Credits

Photo by Joshua Woroniecki on Unsplash

The cost of adding a feature isn’t just the time it takes to code it. The cost also includes the addition of an obstacle to future expansion. The trick is to pick the features that don’t fight each other.

John Carmack

Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20

#codenewbie #programming #quotes #software

This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code

Maxi Contieri ・ May 21 '21

#codenewbie #tutorial #codequality #beginners

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