Is it possible to have an FME parameter read attributes from a feature class that has been defined in a previous attribute?

So, in other words, I when selecting the Prompt and Run option, the user chooses a feature class. In the below example, it's a feature class from a geodatabase, but could just as easily be any format. Once they choose the feature class, I want a dropdown to appear showing the list of attributes that are in that feature class.

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This would be similar to the functionality in an ArcGIS tool that has a derived parameter.

I was wondering if a python parameter could read the attributes and then return a list for the user to choose.

Is this even possible in FME?

1 Answer 1


Interesting question. I'm reasonably confident the answer is no. I've had a few cases where I basically wanted to do this and ended up having to create a convoluted workbench to pull one of a number of possible attributes (i.e. various spellings of "PostCode" "postcode" "POSTCODE " "Post code" etc).

It's probably worth emailing [email protected] and making it a feature request.

I don't think Python parameters are parsed until runtime, so that won't help.

The closest I can think of is maybe some way to do it with FME Server and the API. Maybe. But that's just a pie-in-the-sky notion.

Alternately, if you are trying to find "How have you mis-spelt postcode today" (or some variant therefore), you can use the attributeCopier (and possibly renamer).

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Even though in this instance, only creation_instance has a value, that value is copied into actual_postcode_value because FME will use the default value if the source attribute is a Null.

Note that you'll need to use an AttributeExposer first to expose all attributes shown in the dialog.

  • 1
    That's what I figured. I don't think your method will help me as the field names might not be known until run-time.
    – Fezter
    Mar 2, 2015 at 4:12

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