Apex Enum Patterns

Apex Enum Patterns

Apex enums are simpler than Java enums — no constructors, no methods on enum constants, no per-value data — but they still beat unstructured strings for state-machine dispatch, message routing, and any "one of N exhaustive options" code path.

The mistakes follow a predictable pattern: people serialize enum values into Custom Metadata or a Long Text field, the picklist gets renamed, and Enum.valueOf(String) starts throwing System.NoSuchElementException in production. Or someone adds a new enum value and the switch on doesn't have a branch — Apex falls through silently because there's no compiler exhaustiveness check.

This skill covers the patterns that make enums useful in Apex without the foot-gun.

Recommended Workflow

1. Decide if an enum is the right shape. If you have <2 values or values change at runtime, use a Boolean or a Custom Metadata-driven string. Enums are for closed sets.
2. Name the enum after intent, not type. RenewalAction beats EnumType1.
3. Use switch on <Enum> with a when else branch that throws a clear exception. This is the only way to surface a missed case at runtime when the enum gains a new value.
4. Wrap Enum.valueOf(String) in a safe converter that returns a default or throws a typed exception with the offending input in the message.
5. Document global vs public in managed packages. Once shipped, removing or renaming a global enum value is a breaking change.
6. Write a test that asserts the enum's values() matches the expected set. This is the cheapest exhaustiveness check Apex gives you.

When To Reach For An Enum

The right places: trigger-handler dispatch keys, message-routing discriminators, log-level enums, status machines that the app itself owns end-to-end. Anywhere the set of values is a property of the code, not the data, an enum is the cheaper, safer choice.

The wrong places: anything an admin should be able to add to. If adding a new "approval reason" should not require a deployment, do not put it in an enum. The enum becomes a maintenance ratchet that pulls every dispatcher into the release pipeline.

What This Skill Does Not Cover

• Picklist-field design — see admin/picklist-design.
• Custom Metadata as configuration store — see apex/custom-metadata-types.
• State machines with side effects — see architect/state-machine-patterns.