How do you control which attributes are exposed to the transformers in a custom transformer or output from the custom transformer?

• A. Double-click on the Transformer Input or Transformer Output port and check/uncheck the attributes
• B. Navigator > Transformer Parameters > Group By
• C. Tools > FME Options
• D. Use an AttributeExposer before the custom transformer input and output port(s)

Answer: (A)

Controlling which attributes are exposed to a transformer is done at the port level. Open the Transformer Input or Transformer Output port, and you’ll see a list of attributes associated with that port. Checking or unchecking attributes determines which ones are passed into the transformer (input) or handed to downstream transformers (output). This per-port setting narrows the attribute set that travels through the transformer, keeping data lean and the workflow clearer.

Other options aren’t the standard way to manage port exposure. A global path like Navigator > Transformer Parameters > Group By isn’t about attribute exposure. Tools > FME Options affects the workspace globally, not per port. An AttributeExposer can be used in some contexts, but the direct port-based check/uncheck is the primary method to control exposure for a custom transformer’s input and output.