Refactoring 002 — Extract Method

Find some code snippets that can be grouped and called atomically.

Image by Hreisho from Pixabay

TL;DR: Group your cohesive sentences together

Problems Addressed

• Readability
• Complexity
• Code Reuse

Related Code Smells

Code Smell 03 — Functions Are Too Long

Code Smell 05 — Comment Abusers

Code Smell 18 — Static Functions

Code Smell 22 — Helpers

Code Smell 74 — Empty Lines

Code Smell 78 — Callback Hell

Code Smell 102 — Arrow Code

Steps

1. Move the code fragment to a separate new method

2. Replace the old code with a call to the recently created method.

Sample Code

Before

object Ingenuity {
 fun moveFollowingPerseverance() {
   //take Off
   raiseTo(10 feet)
 
 //move forward to perseverance
   while (distanceToPerseverance() < 5 feet){
     moveForward() 
   }
 
   //land
   raiseTo(0 feet)
 }

After

object Ingenuity { 
 //1. Move the code fragment to a separate new method 
 private fun takeOff() {
   raiseTo(10 feet)
 }
 
 //1. Move the code fragment to a separate new method 
 private fun moveForwardToPerseverance() {
   while (distanceToPerseverance() < 5 feet){
     moveForward() 
   }
 }
 
 //1. Move the code fragment to a separate new method 
 private fun land() {
  raiseTo(0 feet)
 }
 
 fun moveFollowingPerseverance() {
   takeOff()
   //2. Replace the old code with a call to the recently created   method.
   moveForwardToPerseverance()
   //2. Replace the old code with a call to the recently created method.
   land()
   //2. Replace the old code with a call to the recently created method.
 }
}

Type

[X] Automatic

Many IDEs support this safe refactoring

Limitations

Does not work well if you use meta-programming anti-pattern

Laziness I: Meta-programming

Tags

• Complexity
• Readability

Related Refactorings

• Move method to a new class

This article is part of the Refactoring Series.