“Invalid options on ^subform command” error (Adobe Central Pro)

Here’s a puzzler that looks strange, but that is easy to solve – once you understand a key difference between dynamic templates and static templates, and how Central loads and unloads tempplates.

Situation:
– You have multiple templates that you want to use for processing data
– You can process each template independantly without troubles (data only uses one template)
– When you call different templates (data uses the ^form command), with some combinations of files, you get the following error:
Invalid options on ^subform command

Reason:
You are mixing dynamic templates with static templates

Fix:
Ensure all your templates are fully dynamic by ensuring all fields exist inside subforms

Explanation:
Some of your forms are dynamic, some of them are static. Dynamic forms are created when fields are wrapped in subforms.

Dynamic forms, when compiled, create an embedded Preamble (see this in Output Designer with Ctrl+R, when a form is open)
Static forms do not.

The preamble is basically a set of variable definitions that get stored to a special global variable area.
Preamble variables call subform definitions, which are effectively the structural parts of the template.

When a template is loaded, preamble data is executed which reference form structures – for example, if you have a field called myfield in a subform called mysub, you will get:

^comment -----------------------------------------------------------------
^comment Subform: (mysub)
^comment -----------------------------------------------------------------
^define group:myfield!FldNotAvail \groupG_mysub\fieldmyfield.
^define group:myfield!FldUsed \groupG_mysub\fieldmyfield.

When a new template is loaded, any pre-existing form structures are flushed from memory (the item referred to by the “\groupG_mysub\fieldmyfield” part) – but the global preamble variables (the “group:myfield!FldNotAvail” part) are not : they cannot be distinguished easily from regular data, so they are kept.

When you load a static form, no preamble data exists to overwrite previous preamble information – in this case, the definitions for myfield field.

When in your data, myfield is called for the static field, the dynamic definition is still in memory, causing it to try and access a non-existing structure – hence the error.

A short term solution would be to wrap myfield into a subform – this will cause a dynamic preamble to be created for it, overwriting the other template’s definition of myfield

Long term, the recommendation is
-when using multiple templates, avoid where possible having fields of the same name, across all templates
-do not mix static templates with dynamic templates – if such a situation arises, convert the static forms to dynamic, by grouping them in the appropriate subforms. Preferably, leave no field out of a subform