Rule.io SDK

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Loops

<rc-loop> renders a block of email content once per item in a data feed — news feed, remote URL, custom field, or XML source. The loop's child rc-section is duplicated for each item, up to a configurable maximum.

Without loops, a "recommended products" section featuring five items would require five separately-authored sections, each manually configured with a product image, name, and link. When the product data changes, every section needs updating. A loop describes the section structure once; the renderer fills it in from the feed at send time.

Loop variables ​

Inside the loop, individual fields from the current item are inserted using ::loop-value atoms in rc-text and rc-heading content. A loop-value atom identifies its data source by the loop-value attribute of the enclosing rc-loop, and the specific field by an index name — for example, a news item's title, image URL, or link.

Personalization and limits ​

A loop-type="remote-content" loop fetches data from a URL, and that URL can contain [Subscriber:...] and [CustomField:...] tokens that are resolved per recipient before the request is made. This enables personalized feeds — each subscriber sees items relevant to their history — without pre-generating per-subscriber content.

loop-max-iterations prevents emails from growing uncontrollably. A news feed may have 200 articles; a product catalog could have thousands. Without a cap, the compiled email could become enormous and trigger spam filters or delivery failures. Set a limit that matches the design intent (typically 3–10 items for a newsletter block).