You need to model something optional. Have you tried collections?

TL;DR: Collections are fantastic. And Polymorphic.

Problems

• Null
• If Pollution

Solutions

1. Change the optional attribute to a collection.

Context

If you need to model something that might be missing, some fancy languages will provide optional, nullable, and many other wrong solutions dealing with The Billion Dollar Mistake.

Empty collections and non-empty collections are polymorphic.

Sample Code

Wrong

class Person {
  constructor(name, email) {
    this.name = name;
    this.email = email;
  }

  email() {
    return this.email;
    // might be null    
  }

}

// We cannot use safely person.email()
// We need to check for null explicitly

Right

class Person {
  constructor(name, emails) {
    this.name = name;
    this.emails = emails;
    // emails should allways be a collection. 
    // even an empty one
    // We can check it here
  }

  emails() {
    return this.emails;
  }

  // We can mutate the emails since they are not essential

  addEmail(email) {
    this.emails.push(email);
  }

  removeEmail(email) {
    const index = this.emails.indexOf(email);
    if (index !== -1) {
      this.emails.splice(index, 1);
    }
  }
}

// we can iterate the person.emails() 
// in a loop without checking for null 

Detection

[X] Semi-Automatic

You can detect nullable attributes and change them when necessary.

Tags

• Null

Conclusion

This is a generalization of the null object pattern.

Relations

Code Smell 12 - Null

Maxi Contieri ・ Oct 31 '20

#codenewbie #tutorial #oop

Code Smell 149 - Optional Chaining

Maxi Contieri ・ Jul 16 '22

#javascript #webdev #beginners #programming

Code Smell 19 — Optional Arguments

Maxi Contieri ・ Nov 7 '20

#codenewbie #oop #tutorial

More Info

Null: The Billion dollar mistake

Maxi Contieri ・ Nov 18 '20

#codenewbie #tutorial #programming #webdev

• Null Object Pattern

Disclaimer

Code Smells are just my opinion.

Credits

Photo by Levi Jones on Unsplash

To iterate is human, to recurse divine

Peter Deutsch

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