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CONCEPT

Publish / Subscribe in Runline U

Summary

Publish/subscribe separates the workbook that produces a report from the workbooks and applications that consume it.

Core Idea

A publisher writes report data to a named topic. A subscriber listens for changes to that topic, and a getter reads the current report body.

How It Works

U.PUBLISH sends a range using a report group and report name. U.SUBSCRIBE returns an RTD-backed value that changes when the report updates. A dependent U.GET call reads the current report page. The topic is the shared address connecting all three operations.

Why It Matters

Producers and consumers can live in different workbooks, Excel instances, machines, or applications. They only need to agree on report identity, environment, and any required metadata or secret.

In Excel (Runline U)

Keep the subscription in a stable cell and make U.GET depend on that cell. This preserves Excel's dependency chain: an incoming notification updates the subscription cell, which causes the getter and its dependents to recalculate.

Common Patterns

  • Publish a range from one workbook and retrieve it in another.
  • Publish once and support multiple subscribers.
  • Use U.TOPICS_REPORT and U.TOPIC to diagnose address mismatches.

Misconceptions

  • U.SUBSCRIBE is the notification path; U.GET retrieves the report body.
  • A report is not identified by its name alone: report group and environment can also affect the topic.