# Passing a variable to expression section on a rule-based row filter node

**URL:** <https://forum.knime.com/t/passing-a-variable-to-expression-section-on-a-rule-based-row-filter-node/24750>\
**Category:** KNIME Analytics Platform\
**Created:** [June 22, 2020, 11:27pm UTC](https://forum.knime.com/t/passing-a-variable-to-expression-section-on-a-rule-based-row-filter-node/24750 "2020-06-22T23:27:20Z")\
**Posts on this page:** 1\
**Showing post:** 8

<div class="post-metadata">

**Author:** ![ipazin](https://forum-cdn.knime.com/user_avatar/forum.knime.com/ipazin/32/806_2.png) [@ipazin](https://forum.knime.com/u/ipazin)\
**Post date:** [June 24, 2020, 11:49am UTC](https://forum.knime.com/t/passing-a-variable-to-expression-section-on-a-rule-based-row-filter-node/24750/8 "2020-06-24T11:49:11Z")

</div>

Hi @gcfleury,

that is a sign for flow variable type collection holding string values - kind of “list of flow variables”. If you have a collection column type in your table using [Table Row to Variable](https://kni.me/n/_pUeaJb6ZvLqcV7) will create a collection flow variable. See here for more info and example workflow: [How to send dynamic email attachments?](https://forum.knime.com/t/how-to-send-dynamic-email-attachments/20107/12)

Br,  
Ivan

---

_[View the full topic](https://forum.knime.com/t/passing-a-variable-to-expression-section-on-a-rule-based-row-filter-node/24750)._