Q:

Create Published Parameter as a Transformer Output

Using FME 2017 Desktop with ArcGIS 10.2.1 & Oracle 12c.
I am filtering features using a WHERE clause which has a LAST_RUN_DATE being read from a control table.
I am using a SDE reader to get the LAST_RUN_DATE which feeds into another transformer but in some scenarios, like using SQLCreator where there is no input port, it cannot be used unless published as a parameter or hard-coded.
I have now created a published parameter which I am populating before every run - manually.
My question is - can the output of my reader be creating or populating a Published Parameter?

A:

No, as far as I know you can't update User Parameters when running the workspace. Parameters are designed to set before running the workspace.
If you really really really need this you can workaround it using a WorkspaceRunner to fire a child workspace, which you can start with the parent workspace defined published parameters, fed by attributes.
But why not simply use a SQLExecutor instead, which is the same transformer as the SQLCreator but does have a inputport and can be fed by attributes.

As a pro tip, you also can use a FeatureReader, which is in most cases the same as a specific Reader, but with an inputport to initiate it. If you don't have an initiator, use a Creator to start it.

