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0ad92cad86
Correct wording in five events articles to reflect that AL event subscribers bind by parameter name, not position: - add-new-event-parameters-at-the-end: drop the inaccurate claim that appending a parameter forces subscribers to be updated or causes wrong values; keep the append-at-end best practice. - do-not-add-ishandled-to-an-existing-event: reframe from "breaking change" to the semantic/purpose shift that leaves existing subscribers pointless; rename the breaking-change keyword to semantic-change. - name-events-by-publisher-position: extend the good sample with position-named publishers raised from table and report trigger contexts. - initialize-ishandled-to-false-before-publishing: scope the detection and best practice to events that actually carry a var IsHandled, so an OnBefore with no IsHandled is not flagged. - do-not-bypass-critical-operations-with-ishandled: add a litmus-test definition of a critical operation (code that cannot stand as an independent, self-contained unit). Knowledge-only; no contract or wiring change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
26 lines
2 KiB
Markdown
26 lines
2 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [ishandled, initialization, deterministic, onbefore, reset, integration-event, control-flow]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Initialize IsHandled to false before publishing
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## Description
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A routine that raises an `OnBefore…` integration event with a `var IsHandled: Boolean` parameter passes that variable in by reference, so its incoming value decides whether the default logic is skipped. A freshly declared Boolean starts as `false`, but the same variable is frequently reused to raise several events in one routine, and after the first raise it may already be `true`. Assigning `IsHandled := false;` on the line immediately before every raise makes the control flow deterministic and self-documenting, and prevents a stale `true` from silently suppressing logic the author never meant to make skippable. Generated code often reuses one `IsHandled` across several raises without resetting it.
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## Best Practice
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Set `IsHandled := false;` immediately before each `OnBeforeX(…, IsHandled)` raise, then guard the default logic with `if IsHandled then exit;` or `if not IsHandled then …`. Do this even when the variable was just declared: the explicit reset documents intent and stays correct if a second event raise is added to the routine later. This applies only to events that carry a `var IsHandled: Boolean`; an `OnBefore` event with no `IsHandled` parameter needs no reset.
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See sample: `initialize-ishandled-to-false-before-publishing.good.al`.
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## Anti Pattern
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Raising `OnBeforeX(…, IsHandled)` with a variable whose value carries over from an earlier raise, so a subscriber that handled the first event unintentionally suppresses the second routine's default logic. Detection: an `IsHandled` variable passed to more than one event in a routine without an intervening `IsHandled := false;`, or any `OnBefore…` raise that passes an `IsHandled` variable without an intervening `IsHandled := false;`.
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See sample: `initialize-ishandled-to-false-before-publishing.bad.al`.
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