CSC/ECE 517 Fall 2009/wiki 1a 7a HJ

Definition of code refactoring

According to Wikipedia: "Code refactoring is the process of changing a program's internal structure without modifying its external functional behavior or existing functionality with the goals of readability, maintainability, performance, extensibility and simplicity."

Goals of refactoring

Refactoring is motivated by the difficulty of adding new functionality to a program. or fixing a bug in it.

As we said berfore, after code refactoring, the program does the the exact same thing it did before.

The differences are that the new code:

1) is easier to read and so to understand

2) contains less duplication

3) is less complex

4) is more flexible towards future changes

5) could lead to a faster compilation time

Common Refactorings Tools

Here is a list of some examples of refactoring techniques used. For further information, the reader please refer to Lecture 3 of CSC 517 of Dr. Gehringer [1] inspired of the site [2] and to the section 2.1.2 of the thesis of Thomas Corbat [3].

1) Rename : Methods, Fields, Packages, Projects, Parameters, Local Variables

2) Encapsulate Field

3) Move : Method, Field

4) Pull up : Field, Method

5) Push down : Field, Method

6) Extract : Method, Class, Constant, Local Variables

7) Convert Local Variables to Field

8) Change Method Signature

Examples of Refactoring for JAVA

Here are some examples of Refactoring for JAVA

1) Rename

First code

public class rename_Method {

   static void WrongRenameMethod() {
       System.out.println("NC State");
   }

}

Refactor by renaming

public class rename_Method {

   static void ncsu(){
       System.out.println("NC State");
   }

}

2) Encapsulation

Examples of refactoring for Ruby

1) Rename

def FirstMethod

    puts("NC State");

end

Refactor by renaming

def NCSU

    puts("NC State");

end

2) Encapsulation

Current Ruby IDE and Refactoring

The following Current Ruby IDE do not support refactoring :

Ruby in Steel

Arachno Ruby

FreeRIDE

Mondrian Ruby IDE

RubyMine and Eclipse with Aptana are the only current Ruby IDE with refactoring support.

Ruby and JAVA Refactoring Tools : a small comparaison

Comparaison of Refactoring Tools

JAVA	Ruby
Rename	Rename
Move	Move
Extract Class	Convert Local Variable or Field
Extract Super Class	Extract Constant
Encapsulate Field
Introduce Parameter

The differences between the two languages JAVA and Ruby is the number of methods available for refactoring. JAVA has two times more options for refactoring. However, refactoring tools for both JAVA and Ruby are integrated into some IDE like Eclipse.

References

[1] Refactoring and version control, CSC517, NCSU, Dr. Ed Gehringer

   http://courses.ncsu.edu/csc517/common/lectures/notes/lec3-f09.pdf

[2] http://www.refactoring.com

[3] Refactoring Support for the Eclipse Ruby Development Tools

   HSR, University of Applied Science Rapperswil  
   Diploma Thesis of Thomas Corbat, Lukas Felber and Mirko Stocker
   Summary :  http://subs.emis.de/LNI/Proceedings/Proceedings106/gi-proc-106-039.pdf
   Complete Thesis:  http://r2.ifs.hsr.ch/rubyrefactoring.pdf