Yet more code smells? More? Where do they come from?
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.
Previous Parts
Let's continue...
Code Smell 56 - Preprocessors
We want our code to behave different on different environments, operating systems, so taking decisions at compile time is the best decision, isn't it?.
Problems
- Readability
- Premature Optimization
- Unnecessary complexity
- Debugging
Solutions
- Remove all compiler directives.
- If you want different behavior, model it with objects
- If you think there's a performance penalty, make a serious benchmark instead of doing premature optimization.
Sample Code
Wrong
#if VERBOSE >= 2
printf("trace message");
#endif
Right
if (runtimeEnvironment->traceDebug()){
printf("trace message");
}
## even better with polymorphism and we avoid annoying ifs
runtimeEnvironment->traceDebug("trace message");
Detection
This is a syntactic directive promoted by several languages, therefore it is easy to detect and replace with real behavior.
Tags
- Compilers
- Metaprogramming
Conclusion
Adding an extra layer of complexity makes debugging very difficult. This technique was used when memory and CPU were scarce. Nowadays, we need clean code, and we must leave premature optimization buried in the past.
Bjarne Stroustrup, in his book The Design and Evolution of C++, regrets on the pre-processor directives he created years before.
More info
C++ is designed to allow you to express ideas, but if you don't have ideas or don't have any clue about how to express them, C++ doesn't offer much help.
Bjarne Stroustrup
Code Smell 57 - Versioned Functions
sort, sortOld, sort20210117, workingSort, It is great to have them all. Just in case
Problems
- Readability
- Maintainability
Solutions
- Keep just one working version of your artefact (class, method, attribute).
- Leave time control to your version control system.
Sample Code
Wrong
findMatch()
findMatch_new()
findMatch_newer()
findMatch_newest()
findMatch_version2()
findMatch_old()
findMatch_working()
findMatch_for_real()
findMatch_20200229()
findMatch_thisoneisnewer()
findMatch_themostnewestone()
findMatch_thisisit()
findMatch_thisisit_for_real()
Right
findMatch()
Detection
We can add automatic rules to find versioned methods with patterns.
Like many other patters we might create an internal policy and communicate.
Tags
- Versioning
Conclusion
Time and code evolution management is always present in software development. Luckily nowadays we have mature tools to address this problem.
Credits
That's why I write, because life never works except in retrospect. You can't control life, at least you can control your version.
Chuck Palahniuk
Code Smell 58 - Yo-yo Problem
Searching for a concrete method implementation? Go back and forth, up and down.
TL;DR: Don't ab(use) hierarchies.
Problems
- Deep Hierarchies
- Subclassification for Code Reuse
- Readability
- Low Cohesion
- High Coupling
Solutions
- Favor composition over inheritance.
- Refactor deep hierarchies.
Sample Code
Wrong
<?
abstract class Controller {
}
class BaseController extends Controller {
}
class SimpleController extends BaseController {
}
class ControllerBase extends SimpleController {
}
class LoggedController extends ControllerBase {
}
class RealController extends LoggedController {
}
Right
<?
interface ControllerInterface {
}
abstract class Controller implements ControllerInterface {
}
final class LoggedControllerDecorator implements ControllerInterface {
}
final class RealController implements ControllerInterface {
}
Detection
Any linter can check for suspects against a max depth threshold.
Tags
- Hierarchy
Conclusion
Many novice programmers reuse code through hierarchies. This brings high coupled and low cohesive hierarchies.
Johnson and Foote established in their paper this was actually a good design recipe back in 1988. We have learned a lot from there.
We must refactor and flatten those classes.
More info
An error arises from treating object variables (instance variables) as if they were data attributes and then creating your hierarchy based on shared attributes. Always create hierarchies based on shared behaviors, side.
David West
Code Smell 59 - Basic / Do Functions
sort, doSort, basicSort, doBasicSort, primitiveSort, superBasicPrimitiveSort, who does the real work?
TL;DR: Shortcuts for mini wrappers shout for better solutions.
Problems
- Readability
- Bad Naming
- Low Cohesion
- Single Responsibility Principle
Solutions
- Use good object wrappers
- Use dynamic decorators
Sample Code
Wrong
<?
final class Calculator {
private $cachedResults;
function computeSomething() {
if (isset($this->cachedResults)) {
return $this->cachedResults;
}
$this->cachedResults = $this->logAndComputeSomething();
}
private function logAndComputeSomething() {
$this->logProcessStart();
$result = $this->basicComputeSomething();
$this->logProcessEnd();
return $result;
}
private function basicComputeSomething() {
/// Do Real work here
}
}
Right
<?
final class Calculator {
function computeSomething() {
// Do Real work here since I am Compute!
}
}
//Clean and cohesive class, single responsibility
final class CalculatorDecoratorCache {
private $cachedResults;
private $decorated;
function computeSomething() {
if (isset($this->cachedResults)) {
return $this->cachedResults;
}
$this->cachedResults = $this->decorated->computeSomething();
}
}
final class CalculatorDecoratorLogger {
private $decorated;
function computeSomething() {
$this->logProcessStart();
$result = $this->decorated->computeSomething();
$this->logProcessEnd();
return $result;
}
}
Detection
We can instruct our static linters to find wrapping methods if they follow conventions like doXXX(), basicXX() etc.
Tags
- Declarativiness
Conclusion
We came across this kind of methods some time in our developer life, We smelled something was not OK with them. Now is the time to change them!
More info
The primary disadvantage of Wrap Method is that it can lead to poor names. In the previous example, we renamed the pay method dispatchPay() just because we needed a different name for code in the original method.
Michael Feathers
Code Smell 60 - Global Classes
Classes are handy. We can call them and invoke them any time. Is this good?
TL;DR: Don't use your classes as a global point of access.
Problems
- Coupling
- Classes are global unless we use Namespaces.
- Name polluting
- Static Methods
- Static Constants
- Singletons
Solutions
- Use namespaces, module qualifiers or similar
- To avoid namespace polluting, keep the Global names as short as possible.
- Class single Responsibility is to create instances.
Sample Code
Wrong
<?
final class StringUtilHelper {
static function reformatYYYYDDMMtoYYYYMMDD($date) {
}
}
class Singleton {
}
final class DatabaseAccessor extends Singleton {
}
Right
<?
namespace Date;
final class DateFormatter {
function reformatYYYYDDMMtoYYYYMMDD(Date $date) {
}
//function is not static since class single responsibility is to create instances and not be a library of utils
}
namespace OracleDatabase;
class DatabaseAccessor {
//Database is not a singleton and it is namespace scoped
}
Detection
We can use almost any linter or create dependency rules searching for bad class references.
Tags
- Globals
Conclusion
We should restrict our classes to small domains and expose just facades to the outside. This greatly reduces coupling.
More info
Write shy code — modules that don't reveal anything unnecessary to other modules and that don't rely on other modules' implementations.
Dave Thomas
We are done for some time (not many).
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!
Send me your own!