“The single most important reason to create a class is to reduce a programs complexity.”
Steve McConnell – Code Complete 2

“Always write code like the person who will maintain it is a serial killer and knows where you live”
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I’m going to assume you know what a class is and how to write one, so if this is not true, I suggest you look that up before reading this article.

So why or when should we create a class?  This is one of those great theoretical questions, but has many real world consequences.  There are many specific reasons to create a class.  McConnell goes into detail identifying many reasons and elaborating on them.  Since I have no desire to transcribe his wonderful book or write a book length article, I’ll point you in his direction after you’ve read this more entry point article.

For a lot of beginning programmers, classes are seen as real world objects.  A button, a menu, or a gallery.  While these are valid to be represented in their own classes, it isn’t the right reason to have put them in a class.  For me a class is everything needed to contain a single responsibility.  So while managing the display and control of a menu is a responsibility, so is parsing an xml file or grouping and representing the data that constitutes an employee.  So creating classes strictly to represent real world objects doesn’t go nearly far enough. Continue reading →