The Lift-Up Conditional

The Lift-Up Conditional is a refactoring technique useful in those situations when a conditional logic consisting of several cases is mixed in the shape of a mess of nested conditions.

I came across it recently thanks to the local Coding Dojo organized by CraftersVigo, and I must confess I was left with my mouth open.

This technique is better shown than explained, but I’ll try to summarize the process and then include a couple of videos demonstrating it.

1. First, you need full test coverage of your code and a way to visualize it in your IDE.
2. Second, you need to isolate the messy code block in a separate function or method.
3. Third, you make a hypothesis about a condition that could be isolated from the mess.
4. Fourth, you create a conditional (the Lift-Up one) with that exact condition and you copy the whole messy code in both the if and the else branches, using a temporal extracted method if you want.
5. Fifth, you run your tests again with coverage, the dead code will be marked in red. You delete all the dead code and clean up empty or never-changing conditionals.
6. Sixth, this is when you get astonished with the result.

As promised here you have a couple of videos demonstrating the technique:

• The Gilded Rose kata solved by Emily Bache using this technique (this is the second of a three-part screencast).
• The same kata solved by Gregor Riegler, also using the Lift-Up Conditional refactoring.