[Tutor] code smells: Object-orientation Abusers: switch statements

[Alan Gauld]

I meant to add...

On 04/01/14 20:47, Alan Gauld wrote:

> Its called polymorphism and is one of the most powerful advantages of
> OOP since case or switch statements are one of the most fault prone
> structures in procedural programming.
> ...
> Without OOP you would need to do something like
>
> for shape in shapes:
>      if shape['type'] == CIRCLE:
>          result = circle_area(shape['radius'])
>      elif shape['type'] == SQUARE:
>          result = square_area(shape['length'])
>      elif ....
>
> But with OOP we simply call each shapes area method and
> the interpreter works out which method to call:
>
> for shape in shapes:
>   result = shape.area()

This reduction in code in switch statements (and similar savings in 
other scenarios) is one of the reasons that OOP solutions are often much 
shorter than non OOP programs for non-trivial cases.

Beginners often don't see these benefits because their short programs 
only have one or two classes and the overhead of creating the classes 
dwarfs the savings that might accrue. But in a big project where lots of 
if/else type situations may arise the code savings can easily add up to 
20-30%.

HTH
-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.flickr.com/photos/alangauldphotos