Code Smell 122 - Primitive Obsession
Objects are there for the picking. Even the smallest ones.
TL;DR: Use small objects instead of primitive ones.
Problems
Code Duplication
Small Objects Missing
Fail Fast principle violation.
Subset violations: Emails are a subset of strings, Valid Ages are a subset of Real, Ports are a subset of Integers, etc.
We spread Logic and Behavior in many places.
Premature Optimization.
Solutions
Create Small Objects
Build missing abstractions using MAPPER
Use Value-Objects.
Context
We are very lazy to create small objects.
We are also lazy to separate What and How
We like very much to understand the internals of how things work.
We need to start thinking in a whitebox way and looking at the protocol and behavior of small components.
Sample Code
Wrong
//Samples borrowed with permission from
//https://towardsdev.com/why-a-host-is-not-a-string-and-a-port-is-not-an-integer-595c182d817c
var port = 8080;
var in = open("example.org", port);
var uri = urifromPort("example.org", port);
var address = addressFromPort("example.org", port);
var path = pathFromPort("example.org", port);
Right
//Samples borrowed with permission from
//https://towardsdev.com/why-a-host-is-not-a-string-and-a-port-is-not-an-integer-595c182d817c
const server = Port.parse(this, "www.kivakit.org:8080");
//Port is a smallobject with responsibilities and protocol
let in = port.open(this);
const uri = port.asUri(this);
const address = port.asInetSocketAddress();
const path = port.path(this, "/index.html");
Detection
[X] Manual
We can automate checks on constructors for small objects missing opportunities.
Tags
- Primitive Obsession
Conclusion
We need to transform our strings, numbers, and arrays into small objects
Relations
More Info
Credits
Photo by K. Mitch Hodge on Unsplash
Iteration allows us to progressively approach some goal. We can discard the steps that take us further away and prefer the steps that move us nearer. This is in essence how evolution works. It is also at the heart of how modern machine learning (ML) works.
Dave Farley
This article is part of the CodeSmell Series.