I’m writing this post as contribution to the Campagna Anti-IF (Anti-IF Campaign).

Problem

I’m developing an internal Rails plugin for widgets, it provides a class called Widget (really unconventional :-P), and each widget should inherit from it. The actual implementation provides a callback called before_render, that allows to add some logic to a widget, if implemented it’s called before the widget rendering.

Ruby doesn’t have abstract methods, so I have to check if the subclass has the implementation of mentioned method:
# Rendering code.. before_render if respond_to? :before_render # ...

As you can see it’s an inefficient and inelegant way to render the widget, cause we always check if the method was implemented, and because I have introduced an if statement.

Solution

I added to Widget an empty before_render method: if the method it wasn’t implemented into the subclass the rendering code will be safely called. Here the new code:
def before_render end 

# Rendering code..
before_render
# ...