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Cover image for Code Smell 177 - Missing Small Objects
Maxi Contieri
Maxi Contieri

Posted on • Originally published at

Code Smell 177 - Missing Small Objects

We see small primitive data everywhere

TL;DR: Don't forget to model the smallest ones


  • Primitive obsession


  1. find responsibilities for small objects in the MAPPER

  2. Reify them


Since computing early days we map all we see to the familiar primitive data types: Strings, Integers, Collections, etc.

Mapping to dates violates abstraction and fail-fast principles.

in the Wordle TDD Kata, we describe a Wordle word to be different than a String or Char(5), since they don't have the same responsibilities.

Sample Code


public class Person {
    private final String name; 

    public Person(String name) { = name;
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public class Name {
    private final String name; 

    public Name(String name) { = name;
        // Name has its own creation rules, comparison etc.
        // Might be different than a string

public class Person {
    private final Name name; 

    public Person(Name name) {
        // name is created as a valid one,
        // we don't need to add validations here = name;
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[X] Manual

This is a semantic smell. It is related to design activity


In a very small number of mission-critical systems, we have a tradeoff from abstraction to performance.

This is not the usual case. We do premature optimization not relying on a modern computer and virtual machine optimizations.

As always, we need to stick to evidence in real-world scenarios.


  • Primitive


Finding small objects is a very hard task requiring experience to make a good job and avoid overdesign.

There's no silver bullet in choosing how and when to map something.


More Info


Code Smells are just my opinion.


Photo by Shane Aldendorff on Unsplash

The secret to building large apps is never build large apps. Break your applications into small pieces. Then, assemble those testable, bite-sized pieces into your big application.

Justin Meyer

This article is part of the CodeSmell Series.

Top comments (1)

robertotonino profile image
Roberto Tonino

Very interesting! Where would you validate, for instance, Name? Directly in the constructor, with a validate() method, or else?