How can you do two-way Dropbox  local folder syncing on iOS? On my iPhone, I sync my camera photos with Dropbox, so that after I do a photo shoot all the photos are automatically uploaded to my laptop in the Dropbox 'Camera Uploads' folder - ready to sort, edit and delete as necessary.

I now need to be able to do two-way syncing with the iPhone, so that when I delete (or even modify) a photo on the computer, it's also deleted (or modified) from the iPhone's camera photos folder accordingly; this way I'm not left with dozens of 'dud' photos that I no longer want on my iPhone, despite having already deleting them on the laptop. 

The official Dropbox mobile client doesn't allow two-way syncing, so until they introduce such a feature, this can only be possible via a third-party dropbox API-using client.

On Android, I could do this with Dropsync, with many features and full sync customization. Is there an equivalent Dropbox solution for this on iOS?

(I am aware of the idea that iCloud may do two-way syncing built-in, (though am not sure), but I'd like to be able to share the Camera Uploads folder with family members on Windows computers (and even linux), and so find Dropbox a much more multi-platform-friendly service to use for the syncing and collaborating, instead of the iCloud ecosystem.)
Unfortunately, I'm almost certain there's no equivalent Dropbox solution for this currently on iOS.

While I cannot give you a technical reason why two-way syncing on iOS is not possible, I can say that at a high level, the iOS platform is more guarded in terms of allowing developers to access certain capabilities of the device.

As you stated in your question, Android devices are capable of two-way synchronization through apps like Dropsync; this is because of the relatively more open-ended nature of the Android platform for both developers and users. To read more on why this is the case, read the 'Android Offers an Open Platform' section of this article.

To confirm, I contacted two customer representatives of two data-sync companies: Loom and SugarSync. I asked both reps the following question:


  Is possible for two-way synchronization of files between an iOS device and a computer? For example, if I sync pix from my iPhone to my iMac, and then edit/delete the pix on my computer, will the changes be reflected automatically on my iPhone?


Both times, the answer was:


  No, this is not possible due to the closed nature of the iOS platform.


If this capability is very important for your work, I would suggest migrating back to an Android device.

If you want/need to use your iPhone for this, and if you need a platform-independent solution (i.e., you don't want to use iCloud), I'm afraid tedium is in your future. I would suggest that you keep a list of the photos as you edit/delete them on you computer, so that you know which photos have been updated and need to be manually re-download from Dropbox (or manually deleted) on your iPhone when you use it next.