TRAINING : Creating sub-processes

Question

Hello, 
 I am blocked in this tutorial with this error when I'm debugging.

I thing this is about interface rule but I don't understand what is going wrong 
 
 Thank for your help :)

jeremyv0001 · Accepted Answer

I found what's wrong. ac! variable is needed instead of pv! value in the first User Input Task. I don't really understand why, if someone can explain it will be nice :)

rachelz290 · Answer

You use AC! variables for forms. Think of this as a local variable vs a global variable (pv!). Activity class parameters are only available on the node in which they are defined, in this way, you can manipulate the data in the ac without changing the value of the pv! if it is needed in another node in parallel.

Dastagiri Dudekula · Answer

As per the error, its saying that the rule name vfm2_approvevehicle() actually takes 8 parameters, but you did not passed any of them. Please provide necessary parameter to execute the function.

aloks0189 · Answer

Adding to above practitioners suggestions, also if you think that the parameters are not mandatory and you don't want to pass the values for these parameters then try defining any one parameter as null() hence all the parameters (8) will be treated as null as mention below: 
 
rule!yourRuleName( 
 yourFirstParamName: null() 
) 
 
Here appian understands that you want want to pass the value for only one parameter and in fact that too is null()