fileUploadField saveInTo

Question

Scenario: I have a created a reusable fileUploadField component which I am planning to use in all existing fileUploadField field in all apps. I have created a rule inputs for all the parameters of the fileUpload field and passing values to the common component while calling it. In saveInTo of the common component I am calling a!startProcess which will run asynchronously(i.e. no activity chaining). 
 Issue: 
 
 When I drag and drop multiple documents to file upload, a!startProcess is being called multiple times. Is this behavior expected? i.e when I upload multiple docs at the same time, saveInTo will execute multiple times? 
 Sometimes, when I upload multiple docs at the same time, getting the following error. (Especially when I upload 3 to 4 docs at the same time) 
 
 Could not display interface. Please check definition and inputs. Interface Definition: Expression evaluation error [evaluation ID = 50518:8f67a] in rule 'aco_fileuploadfield' : An error occurred while executing a save: Expression evaluation error : Attempted to run a second smart service, but only one smart service can be run per expression evaluation. 
 
 Note: I have built this functionality to capture document details across all apps and all upload fields which are already in use. We don't want to change any UI and major changes to existing screens.

Mike Schmitt · Answer

What is your StartProcess call actually doing? Are you passing in the uploaded Doc IDs? Are you doing so one at a time, or as an array? I would note that these would be UN-submitted doc IDs most likely, and if so they probably won't do what you want (unless you're just noting the raw numeric IDs to a DB table or something). Can you share a code snippet of how you're constructing this call, so we don't have to guess?

Mike Schmitt · Answer

So I'm afraid the plain answer here is that this has grown too bloated for its own good - the File Upload Field is already not very flexible sadly, and you're trying to make it do everything all at once. Having a single File Upload Field handle multiple files is already pretty clumsy even when the use case and implementation is strictly kept pretty simple - and i fear this is an example of what happens otherwise. 
 For better or worse I pretty much never use a multiple-enabled upload field anywhere unless i'm doing a VERY SIMPLIFIED bulk upload (and even then it's super rare). All other times I enforce that my forms deal with a single upload at a time (or at least a single upload per instance of the upload field); often I force a "submit" click if possible (or some other commit click etc). Either of these approaches (despite the fact that they would both violate the requisites you laid out) would likely solve the "multiple smart services" issue as the upload field attempts to loop over the newly-uploaded files and inadvertently tries to launch multiple startProcess calls. Sadly I don't think current functionality exists to let you get around this without *some* compromise.