What is the best way to replace or substitute if..else if..else trees in programs?

Question

This question is motivated by something I\'ve lately started to see a bit too often, the if..else if..else structure. While it\'s simple and has its uses, somet

Answer 1

switch statement or classes with virtual functions as fancy solution. Or array of pointers to functions. It's all depends on how complex conditions are, sometimes there's no way around those if's. And again, creating series of classes to avoid one switch statement is clearly wrong, code should be as simple as possible (but not simpler)

Answer 2

In Object Oriented languages, it's common to use polymorphism to replace if's.

I liked this Google Clean Code Talk that covers the subject:

The Clean Code Talks -- Inheritance, Polymorphism, & Testing

ABSTRACT

Is your code full of if statements? Switch statements? Do you have the same switch statement in various places? When you make changes do you find yourself making the same change to the same if/switch in several places? Did you ever forget one?

This talk will discuss approaches to using Object Oriented techniques to remove many of those conditionals. The result is cleaner, tighter, better designed code that's easier to test, understand and maintain.

Answer 3

There's two parts to that question.

How to dispatch based on a value? Use a switch statement. It displays your intent most clearly.

When to dispatch based on a value? Only at one place per value: create a polymorphic object that knows how to provide the expected behavior for the value.