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Dynamic summarizing data

  • November 18, 2025
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cmccollister
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This seems like is should be so simple, but I can’t get it to work! I want to take a CSV file that has Feature Class Names, FieldPrefixs, and Feature types. For example:

FeatureClass, Prefix, FeatureType

Roads, Road, Line

WildLandUrbanInterface, WUI, Polygon.

 

This CSV file will be dynamic, meaning that the Feature Classes that will be summarized will change.

I then have a SummaryPolygon Feature Class which defines the polygons on which to summarize. I want to iterate through the CSV file, summarize the data for each CSV record, and then add two fields with the prefixs (ie Road_Miles, Road_MilesPerAcre or WUI_Acres and WUI_PercentArea) to the SummaryPolygon. I thought the workspace runner would work well for this, but the Child workspace isn’t updating/showing the new fields that were created after each iteration. Meaning the schema isn’t dynamically updating with the two new fields on the next iteration. In my Reader, I have Workflow Options set to Single Merged Feature and Merge Feature Type checked with Merge Filter = * and FilterType = Wildcard.

All of the summarizing part works just fine, I just can’t figure out the iteration component.

Help?!

 

 

Best answer by lifalin2016

From the outset, your procedure doesn’t look FME-like. One generally doesn’t “iterate through” in FME. That might be why you’re getting stuck.

In FME your procedures tend to be more like “atomize-then-aggregate/filter”.

However, there’s a rather undocumented trick, if you have the name of an attribute or field in an attribute by itself. As you often will have in a dynamic setup.

You can utilize and type an expression like @Value(@Value(attr_with_name)) to get the dynamic value of the attribute, who’s name is retrieved from another attribute. This works because expressions in FME are semi-interpreted

Hope this helps.

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    lifalin2016
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    • lifalin2016Influencer
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    • Best Answer
    • March 13, 2026

    From the outset, your procedure doesn’t look FME-like. One generally doesn’t “iterate through” in FME. That might be why you’re getting stuck.

    In FME your procedures tend to be more like “atomize-then-aggregate/filter”.

    However, there’s a rather undocumented trick, if you have the name of an attribute or field in an attribute by itself. As you often will have in a dynamic setup.

    You can utilize and type an expression like @Value(@Value(attr_with_name)) to get the dynamic value of the attribute, who’s name is retrieved from another attribute. This works because expressions in FME are semi-interpreted

    Hope this helps.

    -- Cheers, Lars I.

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