Kotlin Code Smell 1 - Constants and Magic Numbers

#kotlin #codesmells #cleancode #programming

TL;DR: Avoid using magic numbers without explanation. Their source is unknown, and we fear changing them.

Problems

Coupling
Low testability
Low readability

Solutions

Rename the constant with a meaningful and intention-revealing name.
Replace constants with parameters, allowing them to be mocked from the outside.
The constant definition should be separate from its usage.

Examples

Algorithms Hyper Parameters

Sample Code

Wrong

fun energy(mass: Double) = (mass * 299792458).pow(2)

Right

typealias MetersPerSeconds = Int

// Using a specific unit of measure to avoid another code smell
const val LIGHT_SPEED: MetersPerSeconds = 299792458

fun energy(mass: Double) = (mass * LIGHT_SPEED).pow(2)

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