More code smells. No joke.
We see several symptoms and situations that make us doubt the quality of our development.
Let's look at some possible solutions.
Most of these smells are just hints of something that might be wrong. They are not rigid rules.
This is part V. Part I can be found here, Part II here, Part III is here, Part IV here, part V, VI, VII, VIII and IX.
Let's continue...
Code Smell 46 — Repeated Code
DRY is our mantra. Teachers tell us to remove duplication. We need to go beyond.
Photo by Sid Balachandran on Unsplash
Problems
- Code Duplication
- Maintainability
- Don’t Repeat Yourself
Solutions
- Find repeated patterns (not repeated code).
- Create an abstraction.
- Parametrize abstraction calls.
- Use composition and never inheritance.
- Unit test new abstraction.
Sample Code
Wrong
Right
Detection
Linters can find repeated code.
There are not very good finding similar patterns.
Maybe soon machine learning will help us find such abstractions automatically.
For now, it is up to us, humans.
Examples
Tags
- Duplication
Conclusion
Repeated code is always a smell.
Copying and pasting code is always a shame.
With our refactoring tools, we need to accept the duplication remove challenge trusting our tests as a safety net.
More info
Copy and paste is a design error.
David Parnas
Code Smell 47 — Diagrams
Diagrams are not code. They cannot be a code smell. They are just Diagram Smells.
Photo by Nick Seagrave on Unsplash
Problems
- Maintainability
- Trash code
- Code Duplication
- Diagrams focus only on structure (accidental) and not behavior (essential).
Solutions
- Use diagrams only to communicate ideas with other humans.
- Program on your favorite IDE.Thrash all diagrams.
- Even the ones generated from the source code.
- Trust your tests. They are alive and well maintained.
- Use Domain Driven Design technique.
Sample Code
Wrong
Right
Detection
We can remove all code annotations and forbid them by policy.
Examples
Conclusion
Designing is a contact sport. We need to prototype and learn from our running models.
Papers and JPGs don’t run. They live in the utopic world where everything works smoothly.
CASE was a very hot trend back in the 90s. No good system was developed with these tools.
More info
The Diagram is Not the Model. The model is not the diagram. It is an abstraction, a set of concepts and relationships between them.
Eric Evans
Code Smell 48 — Code Without Standards
Working on a solo project is easy. Unless you go back to it after some months. Working with many other developers requires some agreements.
Photo by De Jesus de Blas — Russia
Problems
- Maintainability
- Readability
Solutions
- Automate your styles and indentation.
- Enforce agreed policies.
Sample Code
Wrong
Correct sample taken from Sandro Mancuso’s bank kata
Right
The right example has several other smells, but we keep it loyal to its GIT version in order to show only code standardization issues.
Detection
Linters and IDEs should test coding standards before a merge request is approved.
We can add our own naming conventions related to Objects, Classes, Interfaces, Modules etc.
Examples
Tags
- Standardization
Conclusion
Use coding standards in your projects.
A well-written clean code always follows standards about naming conventions, formatting and code style.
Such standards are helpful because they make things clear and deterministic for the ones who read your code, including yourself.
Code styling should be automatic and mandatory on large organizations to enforce Collective Ownership.
More info
The nice thing about standards is that there are so many to choose from.
Andrew S. Tannenbaum
Code Smell 49 — Caches
Caches are sexy. They are a one-night stand. We need to avoid them in a long-term relationship.
Photo by Aimee Vogelsang on Unsplash
Problems
- Coupling
- Testability
- Cache invalidation.
- Maintainability
- Premature Optimization
- Erratic Behavior
- Lack of transparency
- Non-Deterministic behavior
Solutions
- If you have a conclusive benchmark and are willing to pay for some coupling: Put an object in the middle.
- Unit test all your invalidation scenarios. Experience shows we face them in an incremental way.
- Look for a real world cache metaphor and model it.
Sample Code
Wrong
Right
Detection
This is a design smell.
It will be difficult to enforce by policy.
Tags
- Premature Optimization
Conclusion
Caches should be functional and intelligent.
In this way we can manage invalidation.
General purpose caches are suitable only for low level objects like operating systems, files and streams.
We shouldn’t cache domain objects.
This page is hosted on a cached website.
More Info
There are only two hard things in Computer Science: cache invalidation and naming things.
Phil Karlton
Code Smell 50 — Object Keys
Primary keys, IDs, references. The first attribute we add to our objects. They don’t exist in the real world.
Photo by Maurice Williams on Unsplash
Problems
- Coupling
- Accidental Implementation
- Bijection Principle Violation.
Solutions
- Reference object to objects.
- Build a MAPPER.
- Only use keys if you need to provide an external (accidental) reference. Databases, APIs, Serializations.
- Use dark keys or GUIDs when possible.
- If you are afraid of getting a big relation graph use proxies or lazy loading.
- Don’t use DTOs.
Sample Code
Wrong
Right
Detection
This is a design policy.
We can enforce business objects to warn us if we define an attribute or function including the sequence id.
Tags
- Accidental
Conclusion
Ids are not necessary for OOP. You reference objects (essential) and never ids (accidental).
In case you need to provide a reference out of your system’s scope (APIs, interfaces, Serializations) use dark and meaningless IDs (GUIDs).
More info
The nice thing about standards is that there are so many to choose from.
David Wheeler
We are done for some time.
But we are pretty sure we will come across even more smells very soon!
I keep getting more suggestions on twitter, so they won't be the last!