Yet another global access coupled with laziness.

TL;DR: Don't use static functions. They are global and utilities. Talk to objects instead.

Problems

• Coupling

• Testability

• Protocol Overloading

• Cohesion

Solutions

• Class Single Responsibility Principle is to create instance. Honor it.

• Delegate method to instance.

• Create stateless objects. Don't call them helpers.

Examples

• Static class methods

• Static attributes

Sample Code

Wrong

class DateStringHelper {
   static format(date) {
     return date.toString('yyyy-MM-dd'); ;    
  }
}


DateStringHelper.format(new Date());

Right

class DateToStringFormatter {
   constructor(date){
      this.date = date;
   }

   englishFormat() {
     return this.date.toString('yyyy-MM-dd');    
  } 
}

new DateToStringFormatter(new Date()).englishFormat()

Detection

We can enforce a policy to avoid static methods (all class methods but constructors).

Tags

• Global

• Libraries

Conclusion

Class are globals disguised. Polluting their protocol with "library methods" breaks cohesion and generates coupling. We should extract static with refactorings.

In most languages, we cannot manipulate classes and use them polymorphically, so we can't mock them or plug them on tests.

Therefore, we have a global reference too difficult to decouple.

Relations

More info

• Single Responsibility Principle

Credits

Photo by Alex Azabache on Unsplash

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There is no programming problem that can't be solved with one more level of indirection.

John McCarthy

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This article is part of the CodeSmell Series.

Last update: 2021/06/28