bcquality/community/knowledge/architecture/posting-routines-must-follow-check-post-line-batch-pattern.md

bc-version	domain	keywords	technologies	countries	application-area
all	architecture	posting-routine check-line post-line post-batch companion-codeunit sales-post yes-no-wrapper journal	al	w1	all

Posting routines must follow the Check Line / Post Line / Post Batch pattern

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Description

Every journal-based posting routine in Business Central is split across three companion codeunits with distinct, non-overlapping responsibilities: <X> Check Line validates one line and shows no UI beyond errors; <X> Post Line writes exactly one line to the ledger/register tables and never touches the Journal table itself, which is what lets other posting code call it directly; <X> Post Batch is the only one of the three that reads and updates the Journal table, looping Check Line then Post Line across all lines. A document posting routine (such as Sales-Post) calls Post Line directly per document and bypasses Post Batch entirely. A new posting routine that conflates these responsibilities, or a page that calls a -Post codeunit directly instead of through its -Post (Yes/No) confirmation wrapper, breaks assumptions other extensions and unattended batch-posting reports rely on.

Best Practice

Keep Check Line free of side effects beyond validation and a first-call-only re-read of setup data; keep Post Line operating purely on the record variable it's given, never on the Journal table, so other posting code can call it without fabricating a journal line first; let only Post Batch read and write the Journal table. Route every page-initiated post through a -Post (Yes/No) wrapper that confirms with the user and then calls the interaction-free -Post codeunit, so the same posting logic stays safely callable from an unattended batch report.

Anti Pattern

A Post Line codeunit that reads back from the Journal table, or a Check Line codeunit that writes to the database on every call, has taken on its neighbor's responsibility and can no longer be reused safely by other posting code. A page wired directly to a -Post codeunit — skipping the -Post (Yes/No) wrapper — either shows no confirmation to the user, or, if confirmation is bolted onto the core codeunit instead, makes that codeunit impossible to call from an unattended process.