Maxi Contieri

Posted on Nov 28, 2020 • Edited on Nov 5, 2021 • Originally published at maximilianocontieri.com

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

#oop #webdev #tutorial #codenewbie

First programming lesson: Control structures. Senior developer lesson: avoid them.

Problems:

Too many decisions together
Coupling
Duplicated code
Violation of Open/Closed Principle.
A new condition should not change the main algorithm.
Nulls

Solutions

Polymorphism
Create hierarchies/compose objects following Open closed principle.
Use State pattern to model transitions.
Use Strategy Pattern/Method Object to choose for branches.

Examples

Discrete Values
State transition
Algorithm choice.

Sample Code

Wrong

	class Mp3Converter {
	convertToMp3(source, mimeType) {
	if(mimeType.equals("audio/mpeg")) {
	this.convertMpegToMp3(source)
	} else if(mimeType.equals("audio/wav")) {
	this.convertWavToMp3(source)
	} else if(mimeType.equals("audio/ogg")) {
	this.convertOggToMp3(source)
	} else if(...) {
	// Lots of new clauses
	}

view raw converters.js hosted with ❤ by GitHub

Right

	class Mp3Converter {
	convertToMp3(source, mimeType) {
	const foundConverter = this.registeredConverters.
	find(converter => converter.handles(mimeType));
	// Do not use metaprogramming to find and iterate converters
	// since this is another problem.
	if (!foundConverter) {
	throw new Error('No converter found for ' + mimeType);
	}
	foundConverter.convertToMp3(source);
	}
	}

view raw decoupledConverters.js hosted with ❤ by GitHub

Detection

Since there are valid cases for If/else usages, we should not pull the plug and forbid these instructions. We can put a ratio of if statements/other statements as a warning instead.