CSC/ECE 517 Fall 2011/ch5 5d he

Automatic Refactoring

Introduction

Refactoring is a technique for restructuring an existing code, altering its internal structure without changing its external behavior. Its done as a series of small transformations. Each transformation does little, but a sequence of transformations can produce a significant restructuring. Since each refactoring is small, it's less likely to go wrong. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring.<ref name="refone"> Refactoring Home Page http://refactoring.com/ </ref> As people make changes to the code to realize their short term goals without fully understanding the design of code, the code loses its structure. The refactoring work is done to remove bits that aren’t really in the right place. Loss of the structure of code has a cumulative effect. The harder it is to see the design in the code, the harder it is to preserve it, and the more rapidly it decays. Regular refactoring helps code retain its shape. <ref name="reftwo"> Why should you Refactor http://sourcemaking.com/refactoring/why-should-you-refactor </ref>

Common Refactoring Techniques

Extraction Refactoring

There are several refactoring techniques related to extraction: Extract method, Extract local variables, extract constants. The first method "Extract method will create a new method from code you've selected. Extract Local Variable refactoring takes an expression that is being used repeatedly and assigns it to a local variable. Extract constant refactoring is to select a static, constant expression, which the refactoring will convert to a static final constant. This is useful for removing hard-coded numbers and strings from your code

Inline Refactoring

This type refactoring is the reverse of local variable extraction, in which we remove a local variable and use the value of the variable(typically an expression) in the place where the variable is used. This can be marginally more efficient than using a temporary variable and, by making the code terser, makes it either easier to read or more cryptic, depending on your point of view<ref name="refthree"> refactoring for everyone http://www.ibm.com/developerworks/library/os-ecref/ </ref>

Encapsulating Fields

Generally its not a good practice to expose the class attributes through public interface. Thus, Encapsulating such fields will make such fields as private or protected as appropriate and generate getters and setters for the associated field.

Changing Method Signature

Here we change the change the parameters, visibility, and return type of a method.

Other Refactorings

There are a multitude of refactorings. Those that are included with RubyMine<ref name="reffour">RubyMine :: Ruby and Ruby on Rails IDE with smart code completion, syntax highlighting and refactoring http://www.jetbrains.com/ruby/features/ruby_ide.html#Refactorings</ref> include:

• Rename refactoring
• Extract Method
• Extract Module
• Extract Superclass
• Introduce Variable
• Introduce Constant
• Introduce Field
• Introduce Parameter
• Inline Variable
• Pull Uo Members
• Push Down Members
• Override Method

Refactoring support in popular IDE(s)

Software	Fully Automatic Refactoring?	Number of Refactorings?
Borland Delphi
Eclipse
Kdevelop
NetBeans
Padre
RubyMine	No	11
Visual Studio

References

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