When Refactoring to a Class

Start with the variables first.

Create the class with only the variables first and then use the new class that contains the variables.

Once that is working, move in the function to the class.

Practical Notes

When doing refactoring it can be helpful to look at a variable that requires refactoring and see what routines it touches.  The routines it touches are possible methods in a refactored class.  (see my work logs notes for this day for an example).

What is the difference between a structure and a class in C++?  http://www.codeguru.com/forum/archive/index.php/t-194315.html

Basically there are a lot of neat stuff like the 'this' pointer, inheritance, polymorphism.  Where would I want to use a structure instead of a class.  In COM I must use a structure.

What does the #pragma once do?  http://en.wikipedia.org/wiki/Pragma_once

It is a non-standard pre-compiler directive which causes the current source file to be only included once in the compile.

Refactoring Study Notes

http://sourcemaking.com/refactoring

Refactoring (noun): a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior.

Refactor (verb): to restructure software by applying a series of refactorings without changing its observable behavior.

 the purpose 

Optimization fits refactor but the code my be harder to understan.

Always be aware of which hat you are wearing.

Tidying up the code.

Regular refactoring help the code maintain its shape.

Eliminate duplicate code.

 Make the code better communicate its purpose.

Design decay

Rule of three:  1st time just do it.  2nd time wince.  3rd time refactor.

When to refactor:

1. add a function
2. fix a bug
3. code review

Small code review, use code.

Large code review, use UML and CRC 

(class-responsibility-collaboration) 

cards.

Design reviews with groups, code review with individuals.

{What about using a random process to select the individual reviewers pairing?}

Ken Beck:  "Programs have two kinds of values:  what they can do for you today and what they can do for you tomorrow."

parasitic indirection - indirection that gives not value

int someValue()

{

   return noValue()

}

int noValue()

{

   return 1;

}

avoid refactoring when close to a deadline. 

OK

Pattern Study - Structural

Design Pattern Grouping:

1. Structural Patterns
1. Adapter
2. Bridge
3. Composite
4. Decorator
5. Facade
6. Flyweight
7. Proxy
2. Creational Patterns
3. Behavioral Patterns

Links:

http://patterns.cs.up.ac.za/

Pattern Study - The Future of

I got this from Judith Bishop book, C# Design Patterns, page 256.

Some problems with design patterns:

• Traceability - hard to maintain when programming language doesn't support the underlying pattern.  Pattern can be spread across several classes.
• Reusability - design pattern is not encapsulated and must be reimplemented each time it is used.  {What about a design pattern template, several template classes that ease the implementation of a pattern?}
• Writability - methods with trivial behavior not support be language can be tedious to write and maintain.
• Maintainability - multiple patterns can lead to a large cluster of mutually dependent classes causing high coupling between the classes.

The current research is how to transform design patterns into reusable artifacts so the programmer doesn't have to implement them over and over again.  {Addressing all the above problems.}

Pattern Study - UML

Class 

• Class
• - attribute
• + operations()

Interface

• <<interface>>
• IClass
• +operations()

Note

• descriptive text

Package (grouping of classes and interfaces

• Package

Inheritance

• A <--- B (horizontal) : B inherits from A

Realization

• A <-- B (horizontal): B implements A

Association

• A --- B: A and B call and access each other's elements

Association (one way)

• A --> B: A can call and access B's elements, but no vice versa

Aggregation

• A <>--- B:  A has a B, and B can outlive A

Composition

• A <<>>--- B:  A has a B, and B depends on A.

Class Versus Interface Inheritance

From "Design Patterns Elements of Reusable Object-Oriented Software" 
1994

There is a difference between a object's class and its type.

Class defines how an object is implemented.

Type defines its interface or the set of requests to which it will respond.

Class inheritance defines an object's implementation in terms of another object's implementation.  A mechanism for code and representation sharing.

Interface inheritance defines or describes when an object can be used in place of another.