Classes are handy. We can call them and invoke them at any time. Is this good?
TL;DR: Don't use your classes as a global point of access.
-
Coupling
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Classes are global unless we use Namespaces.
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Name polluting
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Static Methods
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Static Constants
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Singletons
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Use namespaces, module qualifiers or similar
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Avoid namespace polluting, keep the Global names as short as possible.
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Class single Responsibility is to create instances.
<?
final class StringUtilHelper {
static function reformatYYYYDDMMtoYYYYMMDD($date) {
}
}
class Singleton { }
final class DatabaseAccessor extends Singleton { }<?
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
}We can use almost any linter or create dependency rules searching for bad class references.
- Globals
We should restrict our classes to small domains and expose just facades to the outside. This greatly reduces coupling.
Code Smell 18 - Static Functions
Code Smell 17 - Global Functions
Singleton - The root of all evil
Coupling - The one and only software design problem
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Write shy code — modules that don't reveal anything unnecessary to other modules and that don't rely on other modules' implementations.
Dave Thomas
Software Engineering Great Quotes
This article is part of the CodeSmell Series.