document function is working to get size and extenstion

Question

HI team, 
 
 i want to find the type of extension and Size of list of documents and i have used document function and build an expression rule it is working fine in expression rule as expected when i call that expression in an interfcae it is shoowing error as document function is deleted. 
 a!localVariables(
 local!size: a!forEach(ri!documents, document(fv!item, "size")),
 local!extension: a!forEach(
 ri!documents,
 document(fv!item, "extension")
 ),
 toboolean(
 and(and(reject(
 fn!isnull,
 {
 a!forEach(
 local!extension,
 if(fv!item <> "pdf", false, null)
 )
 }
 )),
 and(reject(
 fn!isnull,
 {
 a!forEach(
 local!size,
 if(fv!item > 5000000, false, null)
 )
 }
 )
 )))
 
) 
 
 when i use in interface getting error as shown below

Mike Schmitt · Answer

vinayj0006 said: i want to disable a button on the above mentioned conditions 
 Unfortunately until something like my Ancient Feature Request is implemented, there is no direct supported way to do this with freshly-uploaded files. The linked feature request would, of course, enable this use case as well as many other things. If you feel so inclined, please visit that old thread, upvote it, and add a comment detailing your use case. 
 cc Peter Lewis (are there any engineers finally ready to take this on as their "free time project"?)

Harsh Kumar Agarwal · Answer

Hi vinayj0006 , 
 a!localVariables(
 local!document,
 local!documentContent,
 local!documentSize,
 local!documentExtension,
 {
 a!fileUploadField(
 label: "Documents",
 target: cons!APP_TEMPORARY_FOLDER,
 maxSelections: 1,
 value: local!document,
 saveInto: {
 local!document,
 a!save(
 local!documentContent,
 property(
 property(
 a!fileUploadField(value: local!document),
 "contents",
 null
 ),
 "value",
 null
 )
 ),
 a!save(
 local!documentSize,
 property(
 local!documentContent,
 "fileSizeDisplay",
 null
 )
 ),
 a!save(
 local!documentExtension,
 property(local!documentContent, "extension", null)
 )
 }
 )
 }
) 
 
 You can use this code to get the metadata of uploaded document at runtime.

Mike Schmitt · Answer

Please note that this method is very unsupported and potentially buggy (and could stop working after any arbitrary update to the behind-the-scenes component code). 
 Prior to the implementation of the file upload field "validations" parameters that enabled validating on these, I considered it (personally) acceptable to use this work-around if only for the sake of validating. However now that we *can* validate on these aspects of uploaded files, directly using supported OOB functionality, I consider it too risky to use in any production sense (and won't personally recommend it or even directly hint at the capability anymore unless it's in a context where i know it'll be used only for testing or experimentation). So I advise extreme caution / reservation , both for anyone considering adopting this approach, as well as for those providing it in threads here.

Mike Schmitt · Answer

Peter Lewis said: I'd be very interested in understanding more about this use case why it is important to disable the button over using the out-of-the-box validation behavior (where it prevents form submission). 
 I can do the "devil's advocate" position on this one pretty easily: it's often desired to have a "Save Changes" button which skips *most* validations but still validates some more important things (for instance, validating that some text fields don't contain database-breaking lengths, or that there aren't files in place that would be problematically large). Since the simple "validation group" concept doesn't actually handle this, one of my personal favorite workarounds is disabling the "save changes" button when something exists that shouldn't be saved. (There was an entire debate about this just earlier this morning in the Discord). But for this use case, of course, even that isn't directly possible.

Mike Schmitt · Answer

Was the document just uploaded by the user on the very same interface?

Mike Schmitt · Answer

This is what I expected based on your error description. Documents which have just been uploaded on the same interface are not available to the normal set of document parsing functions, including "document()", and trying to call it will result in an error. 
 This is because, prior to the form being submitted, the documents are actually stored in a special place in the Appian File System that we don't have access to from the front-end (including the design side). 
 Only after the task is submitted, are they moved out of that reserved space and into their target upload folder, at which point you can call "document()" on them.

Mike Schmitt · Answer

I would add, also, that the File Upload Field has a built-in way to validate on Extension and Size of uploaded files, so there should be no need to implement your own version of it at this point.

document function is working to get size and extenstion

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