Empty files on upload

[Cross-linking for reference: https://stackoverflow.com/questions/66862389/image-upload-to-dropbox-api-from-ios-sends-corrupted-file-to-dropbox ]

The /2/files/upload endpoint is a "content-upload" style endpoint, meaning that it requires the file data to be uploaded in the request body. I see you're attempting to set the file data as such by using the "body" parameter in your "requestOptions" that you pass to "fetch". 

That seems correct, but you'll need to make sure your "file" variable contains the actual file data you want to upload.

I understand you currently just have the URL for local file data though; not the file data itself. You'll need to read the data from the local filesystem in order to pass the data along. I'm afraid I can't offer much guidance on doing so though as that's not related to the Dropbox API itself. You may need to refer to the relevant iOS documentation from Apple (or otherwise React/Expo if they offer functionality for this).