Flutter build IOS on root of my flutter app does not work

The source of my problem was that Flutter could not find the latest installed version of Xcode.

To fix it, go to Xcode->preferences->locations->set value for command Line tools.

The suggestion from flutter doctor -v is quite clear

✗ Xcode installation is incomplete; a full installation is necessary for iOS development.  Download at: https://developer.apple.com/xcode/download/  Or install Xcode via the App Store.  Once installed, run:    sudo xcode-select --switch /Applications/Xcode.app/Contents/Develope

You could try starting Xcode and agree when it asks to install missing components.

Id suggest you try the dev or master channel where support for Xcode 10 should have landed. Otherwise check this suggestion https://github.com/flutter/flutter/issues/20685#issuecomment-413524718

If you Installed Xcode 10 manually via Apple Developer Download Center or Other Sources, then At first, RENAME your Xcode to the Version name you downloaded, like I downloaded the Xcode 10.1 version, so for me the renamed name would be Xcode10.1.app the .app extension is optional as it already has .app extension...

After that, paste this Command on your Terminal,

sudo xcode-select --switch /Applications/Xcode10.1.app/Contents/Developer

Note: the Xcode Version (i.e. Xcode10.1.app ) is Mendatory, if it's there good otherwise, Rename and add it, it's COMPLETELY SAFE and doesn't have any side effects