React Native Fetch Blob - undefined is not an object (evaluating 'RNFetchBlob.DocumentDir')
After linking you need to run
pod update
inside ios folder
So it looks like the module isn't importing. Obvious I know, I can only think of a few things to help seeing as that project looks fairly popular and stable.
I noticed that you're requiring 'react-native-file-uploader' but using 'react-native-fetch-blob'. I'm assuming this is a mistake. You could also try, if you haven't:
var RNFetchBlob = require('react-native-fetch-blob')
Now assuming you're correctly importing it, try one of the following and then restart x-code:
If you haven't already restart the packager. I recall having to restart the packager every time I installed a new module.
If that doesn't work, try installing deleting it from your node modules (just to be safe) and installing with cocoa pods which will handle all of the linking for you.
If you are using React Native >= V.060 nothing to do
If you are using React Native <= 0.59
Check this link : https://github.com/wkh237/react-native-fetch-blob/wiki/Manually-Link-Package