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Cover image for Refactoring 007 - Extract Class
Maxi Contieri
Maxi Contieri

Posted on • Originally published at maximilianocontieri.com

Refactoring 007 - Extract Class

Behavior is repeated across the system. But we are missing a concept

TL;DR: Put together what belongs together

Problems Addressed

  • Code Duplication

  • Missing Abstraction

  • Low Cohesion

Related Code Smells

Steps

  1. Extract the methods (and accidentally the properties) coupled into a new concept

  2. Use the new concept

Sample Code

Before

 final class Person {

      private String name;

      // Below cohesive properties
      private String homeAreaCode;
      private String homeNumber;

      public String name() {
          return name;
      }

      // Below cohesive behaviour
      public String telephoneNumber() {
          return ("(" + homeAreaCode + ") " + homeNumber);
      }
      String areaCode() {
          return homeAreaCode;
      }
      String officeNumber() {
          return officeNumber;
      } 
 }

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After

// 1. Extract the methods (and accidentally the properties) coupled into a new concept      
   public class TelephoneNumber {

      private String number;
      private String areaCode;

      public String telephoneNumber() {
          return ("(" + areaCode + ") " + _number);
      }
      public String areaCode() {
          return areaCode;
      }
      public String number() {
          return number;
      }
   }

final class Person {

      private String name;

      // 2. Use the new concept
      private TelephoneNumber officeTelephone = new TelephoneNumber();

      public String name() {
          return name;
      }
      public String telephoneNumber(){
          return officeTelephone.getTelephoneNumber();
      }

  }


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Type

[X] Automatic

Most IDEs implement this safe refactor.

Why code is better?

Logic code is in just one place together with its rules

Tags

  • Classes

See also

Refactoring.com

Refactoring Guru

Credits

Image from drpepperscott230 on Pixabay


This article is part of the Refactoring Series

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