The Virtual List Technique
ExpertUse the Virtual List pattern to build custom list views, reports, and data displays that go beyond what portals and sub-summary layouts can achieve natively.
What you'll learn
- How the Virtual List architecture works
- How to set up the Numbers utility table and relationship
- How to populate the virtual list via script and display it in a portal
- Practical use cases: custom reports, search results, command logs
The Virtual List technique (developed by Ray Cologon and popularized in the FM community) uses a portal relationship with a numbers/counter table to display arbitrary lines of content in a portal, where each row shows a computed value from a script-populated list. This enables fully custom report layouts, complex list displays, and content that cannot be expressed as a simple portal or sub-summary.
Virtual List architecture overview
The Virtual List uses a portal connected to a Numbers table (rows 1-N). Each portal row evaluates a GetValue() calculation on a global multi-line text field. The script populates the global with newline-separated values; the portal renders one value per row.
// Architecture: // 1. Numbers table: just one field (n), containing integers 1, 2, 3, ... 10000 // 2. Global field: Globals::VL_Content (text, global storage) // 3. Relationship: Globals to Numbers via a "less than or equal to" trick: // Globals::VL_Count >= Numbers::n // (VL_Count = number of lines in VL_Content) // 4. Portal: based on the Numbers TO // 5. Calculation field in portal: GetValue ( Globals::VL_Content ; Numbers::n ) // When the script sets VL_Content to a return-separated list of lines // and VL_Count to the number of lines, the portal shows one line per row
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