I want the same thing as you. I found a little workaround for my most private information which I have started doing. For starters I LOVE that macOS Sierra now allows you to backup your entired Documents folder to iCloud with the the tap of a button. BUT... I have a folder marked "Personal" in my documents folder where I store private information and I don't want that to be available in the iCloud Drive app. So here's what I did...
Using the disk utility app on my Mac I turned my "Personal" folder into a disk image (.dmg) with a password. Since I rarely go into this folder I figured why not. After the conversion I then deleted the folder. Now whenever I need to access this folder I simply open the .dmg file, enter my password, and it is mounted to my computer like any other image. I can then add, remove, edit anything on the image and eject it when I am finished. After ejecting iCloud will automatically make sure the image is up to date in the cloud and I dont have to worry about anyone ever accessing my private files without my image password.
Then over in the app... The folder is gone and replaced with a disk image file which cannot be opened. Again, this may not be the best option for you but in my case I love that I did this to my Personal folder.
because i have an excel file with formula etc in my personal stuff. i need to access this on my iphoneWhy not just place your personal info and stuff in a note and password/Touch ID lock that note? Seems like that would be an easier solution.
i don't remember the apps name, but like 15 years ago on my $100 nokia i could do exactly what you described. every critical setting and personal document was password protected. i still remember that i missed this when i got the very first iphone in 2007. i still missNo, per app TouchID or PIN locking is not supported in iOS9/10. Hopefully it will be system wide for every individual app in 10.1 or 11.x because I don't trust anybody, barely trust myself.. I really want it. It's silly that if you let someone browse some pictures that they get to change my settings, read my email, browse my hidden photos, etc. Let me set a lock, and not like notes, per note, but simply per app.
I'm not gonna place over 10GB of files in a noteWhy not just place your personal info and stuff in a note and password/Touch ID lock that note? Seems like that would be an easier solution.