Maxi ContieriNested or Pseudo-Private Classes seem great for hiding implementation details.
TL;DR: Don't use nested classes
Problems
Bijection fault to real world concepts.
Lack of testability
Lack of reuse
Scopes and namespaces complexity
Solutions
Make the class public
Keep the public class under your own namespace/module.
Use a Facade to the external world to hide it.
Context
Some languages allow us to create private concepts that only live inside a more significant idea.
These classes are harder to test, harder to debug, and reuse.
Sample Code
Wrong
class Address {
String description = "Address: ";
public class City {
String name = "Doha";
}
}
public class Main {
public static void main(String[] args) {
Address homeAddress = new Address();
Address.City homeCity = homeAddress.new City();
System.out.println(homeAddress.description + homeCity.name);
}
}
// The output is "Adress: Doha"
//
// If we change privacy to 'private class City'
//
// We get an error " Address.City has private access in Address"
Right
class Address {
String description = "Address: ";
}
class City {
String name = "Doha";
}
public class Main {
public static void main(String[] args) {
Address homeAddress = new Address();
City homeCity = new City();
System.out.println(homeAddress.description + homeCity.name);
}
}
// The output is "Adress: Doha"
//
// Now we can reuse and test City concept
Detection
[X] Automatic
Since this is a language feature, we can detect it and avoid its usage.
Tags
- Hierarchies
Conclusion
Many features are bloated with complex features.
We seldom need these new pop culture features.
We need to keep a minimal set of concepts.
More Info
Disclaimer
Code Smells are just my opinion.
Credits
Photo by Dana Ward on Unsplash
Developers are drawn to complexity like moths to a flame, frequently with the same result.
Neal Ford
This article is part of the CodeSmell Series.
