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apex-enum-patterns

Apex enum patterns — enum-based dispatch instead of string switching, ordinal stability, enum values in Custom Metadata, package-global enums, and the limitations (no methods on enum constants, no associated data). Covers `Enum.values()`, `valueOf(String)` failures, and the right way to map an enum to/from a picklist value. NOT for picklist-field design and value-set management — use admin/picklist-and-value-sets. NOT for reading picklist values at runtime via describe — use apex/apex-schema-describe.

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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.

  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

Package files