How can one create a custom file upload widget?

I have had a look around everywhere on the docs. If one needs to create a file upload widget instead of a text widget like in this example:  Create an entity e.g MyDocument and generalise it with the System.File.  in the xml file: <property key="file" type="file" required="false"> in mendix studio pro trying to access at leastone attribute from MyDocument of type “file” like in the xml. Nothing is matched in the filter Basically I just want to simply create a custom widget that accepts file uploads. Can this be achieved with mendix? If so how?
1 answers

I believe the current pluggable widgets API allows only for read only access to files. However, it can be done. Perhaps this widget can give you some ideas or is maybe even what you’re looking for:

Source on GitHub: