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- dimension-management-wiring: SaveDefaultDim's third argument is the shortcut dimension number (1-8), not the field's AL field ID; the fixture passed FieldNo(...) = 10. GetDefaultDimID's InheritFromDimSetID must be 0 when recomputing after the linking record changes, not the document's existing Dimension Set ID (which would retain the previous customer's leftover dimensions). Verified against DimensionManagement.Codeunit.al and BankDepositHeader.Table.al in the BCApps reference clone. - check-post-line-batch-pattern: "Post Line writes exactly one line to the ledger" overclaimed - Gen. Jnl.-Post Line alone calls InsertGLEntry from a dozen call sites (balancing entry, VAT, currency rounding, deferrals) and can write several G/L Entries per journal line. Reworded to "posts exactly one journal line" and softened the "distinct, non-overlapping responsibilities" absolute. - namespace-must-be-verified-from-source.bad.al: dropped the "resolves in a local build, fails in VS Code" comment (taught an inherent compiler/language-server disagreement that isn't real); reframed as stale/cached symbols, matching the prose fix already made. - file-datatype-saas.good.al: replaced the deprecated 5-argument UploadIntoStream overload with the current 2-argument one, and actually staged through TempBlob as the article's own Best Practice instructs (the declared TempBlob variable was previously unused). - test-data-must-be-random-and-complete: no longer treats a short-but-valid value as defective merely for being "underfilled" - AL field lengths are maxima, not minimums. Scoped to missing values or a scenario with an explicit length/format requirement (e.g. a truncation test). Updated the al-testing-review.md routing cue to match. - stored-derived-fields-must-not-be-exposed-directly: stopped mandating source-field exposure as part of the core pattern: the good fixture exposed only one of the derived value's two inputs (Hours Used, not Budgeted Hours), making the claimed "so the consumer can verify it" impossible. Reframed as an optional, all-or-nothing addition and fixed the fixture to expose both inputs. Rebased onto upstream/main to resolve conflicts in al-breaking-changes-review.md, al-data-modeling-review.md, al-performance-review.md, and al-style-review.md against merged PRs #148 and #153; all sides' worklist tokens/cues retained.
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Recalculate Stored Derived Fields Before Exposing Them on API Pages
Contributions welcome — open a PR to refine or extend this article.
Description
A stored field whose value is derived from other fields inside an OnValidate trigger only updates when that specific trigger fires. If the underlying source data changes through some other path, the stored value goes stale without raising any error. Exposing such a field directly on an API page hands external consumers a snapshot that may be significantly out of date.
Best Practice
Recalculate the derived value in OnAfterGetRecord from its authoritative source — typically a FlowField — using a page-level variable, and expose that recalculated value instead of the stale stored field. Whether to also expose the source fields is a separate design decision, not a requirement of this pattern; keep the API contract scoped to what consumers actually need. If letting the consumer verify the recalculation is itself a requirement, expose every field the calculation reads, not just one of them — a derived value with two inputs needs both exposed, or the "verification" is incomplete.
See sample: stored-derived-fields-must-not-be-exposed-directly.good.al.
Anti Pattern
Exposing the stored field directly via Rec, trusting that it was kept in sync by whichever trigger last touched it.
See sample: stored-derived-fields-must-not-be-exposed-directly.bad.al.