mirror of
https://github.com/microsoft/BCQuality.git
synced 2026-08-06 17:36:53 +01:00
363f08f47e
* Add P0 extensibility compatibility knowledge Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 645349fd-1892-48f3-8a84-db77d6abd1c3 * Correct event compatibility guidance Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 645349fd-1892-48f3-8a84-db77d6abd1c3 --------- Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
26 lines
1.9 KiB
Markdown
26 lines
1.9 KiB
Markdown
---
|
|
bc-version: [16..]
|
|
domain: interfaces
|
|
keywords: [interface, defaultimplementation, enum-implements-interface, fallback, extensible-enum, implementation-property]
|
|
technologies: [al]
|
|
countries: [w1]
|
|
application-area: [all]
|
|
---
|
|
|
|
# Set DefaultImplementation on an enum so an unmapped value still resolves to an interface
|
|
|
|
## Description
|
|
|
|
An `enum` that `implements` an interface maps each declared value to a codeunit through the `Implementation` property. A declared value, including one supplied by an enum extension, can omit that mapping. Assigning that value to an interface variable then fails at runtime unless the enum provides `DefaultImplementation`. This property is for declared but unmapped values; an ordinal that is no longer declared is a different case covered by `handle-unknown-enum-ordinals-with-unknownvalueimplementation`.
|
|
|
|
## Best Practice
|
|
|
|
On any extensible enum that implements an interface, set `DefaultImplementation = <Interface> = <Codeunit>;` at the enum level, pointing at a safe implementation. Values with their own `Implementation` keep using it; declared values without one resolve to the default. Do not rely on this property for persisted ordinals that match no declared enum value.
|
|
|
|
See sample: `set-defaultimplementation-on-enum.good.al`.
|
|
|
|
## Anti Pattern
|
|
|
|
An extensible `enum ... implements <Interface>` where at least one value sets no `Implementation` and the enum declares no `DefaultImplementation`. Code that assigns that value to an interface variable and invokes a method throws at the call site, and because the enum is extensible the failing value can be introduced by a third party long after the consumer ships. Detection signal: an enum that implements an interface, has a `value(...)` with no `Implementation`, and no enum-level `DefaultImplementation`. Add a `DefaultImplementation` mapping to close the gap.
|
|
|
|
See sample: `set-defaultimplementation-on-enum.bad.al`.
|