Lift-up Conditional

This refactoring was named by Emily Bache. She first learned it from Llewellyn Falco.

Examine

Look for a complex conditional that has a condition that is duplicated in more than one place. This is the conditional you will ‘lift up’ to be only in one place at the top. Note - in this process another conditional might become duplicated instead, so it doesn’t always help.

Prepare

Copy the section of code containing the conditional.

Implement

• Tests all passing
• Select the whole piece of code with the duplicated conditional in, copy to clipboard
• Surround with if/else
• Ensure you have the whole piece of code duplicated in both if and else clause
• Put the conditional you want to ‘lift up’ into the if condition
• All tests passing
• In the ‘if’ section, carefully replace the condition with ‘true’. In ‘else’ section, carefully replace it with ‘false’.
• All tests passing
• Simplify ‘true’ and ‘false’ conditionals
• All tests passing

Clear

Check whether the conditional really is simpler now, if not revert.

Follow up

Once the conditional is clearer, consider extracting and naming parts of it.

Prompted by Code Smells

Relevant Learning Hours

• Lift-Up Conditional Introduction
• Lift-Up Conditional on Gilded Rose

Sources

• This refactoring was contributed to this site by Emily Bache

Back to All Refactorings