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26 lines
1.7 KiB
Markdown
26 lines
1.7 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [on-before, on-after, do-procedure, thin-shell, meth, is-handled, extraction, entry-point]
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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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# CMFRT OnBefore → Do → OnAfter procedure shape
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## Description
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Global procedures in CMFRT Meth codeunits are thin shells: the body consists of firing `OnBefore<Name>` with `var IsHandled: Boolean`, exiting if handled, calling a local `Do<Name>` procedure that holds all business logic, and firing `OnAfter<Name>`. Local variables that only serve the business logic (record buffers, labels, working values) live in the `Do` procedure, not in the shell. This keeps the event bracket structurally impossible to bypass — the `OnAfter` event cannot be skipped by an early `exit` inside business logic, because business logic lives one level down.
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## Best Practice
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Write every global Meth procedure as: reset `IsHandled`, fire `OnBefore`, `if IsHandled then exit;`, call `Do<Name>(...)`, fire `OnAfter`. When review finds a global procedure whose body mixes event calls with business logic, extract the logic into `Do<Name>` and move its private variables and labels along with it.
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See sample: `cmfrt-onbefore-do-onafter.good.al`.
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## Anti Pattern
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A global procedure whose business logic sits inline between the `OnBefore` and `OnAfter` calls. Inline bodies grow early `exit` paths that silently skip the `OnAfter` event, and their local variables and labels accumulate at the shell level where every branch can touch them. Equally wrong: declaring the event pair but never calling the events from the procedure (dead events), which advertises an extension point that never fires.
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See sample: `cmfrt-onbefore-do-onafter.bad.al`.
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