Guard Clauses

Scenario

In this section (and the next), we're working on a backend system that processes orders for a large e-commerce platform.

We're working with code in a background process that needs to check whether an order was paid, canceled, is suspected of fraud, and so on.

As we'll see, it's a little hard to work with due to containing nested conditionals.

Fail Fast

One of the best ways to deal with nested conditionals is to create what are called guard clauses (https://refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html).

In essence, we want to follow a couple of guiding principles:

• Return from our method at the earliest time possible.
• Each condition (if possible) is tested to see whether it fails rather than passes.

Both of these principles combined are sometimes termed fail fast. We want our methods to fail as fast as possible. When our code contains nested conditionals, we are doing the opposite...