How make loop with blocking transformers in fmx?

What are you trying to accomplish? I'm having difficulties understanding the logic.

I have a more complex workspace where I need to loop over a custom transformer containing blocking transformer(s). Having errors with that I reproduced as small as I could here, so it does not really have a purpose :)

Did you go through this tutorial first: https://community.safe.com/s/article/looping-with-blocking-transformers

As well as this: https://s3.amazonaws.com/gitbook/Desktop-Advanced-2019/DesktopAdvanced5CustomTransformers/5.11.CustomTransformerLoops.html

I tried the first tutorial in 2020.1 and experiencing similar errors. Sometimes it seems there is some erratic caching on the port definitions.

Example:

• In the fmx, create a new output port X
• Save
• In host script, delete custom transformer
• Re add custom transformer
• Ensure see linked symbol/color
• The X output is not there!

Other updates do work:

• In fmx, add a Terminator on an existing input port
• Save fmx
• Readd custom transformer
• Run - it terminates proving it has been updated

I have found that blocked looping doesn't work with private input ports. It's annoying as there is no good reason for the loop input to be visible on the custom transformer. I usually name it some variation of DoNotUse.

I am observing the same thing. Wasted a lot of time this afternoon chasing this issue :(

Thanks! Wish this can be fixed soon.

I usually put the looping part in a custom transformer inside the custom transformer when I have to deal with blocking. This spares me of the looping input not being private and editing the transformer in a different instance of FME.

Try it as a workaround if it suits your workflow.

Hi @caracadrian​, I was just wondering if you might be able to provide an example of nested custom transformers being used to work around blocking with looping? I'm trying to build something similar myself but am not having much success. Thanks in advance.

@barrett_h​ take a loop at this one that I uploaded to the fme hub https://hub.safe.com/publishers/caracadrian/transformers/eterra3-ancpi-rogeometryfetcher