How to Debug your App on iOS 10 iPhone with Xcode 7

Running your app on iOS 10 with Xcode 7

When you try to run an app you are building using Xcode 7 (e.g. Xcode 7.3.1) to your iOS 10 device, you are greeted with the error message “Could not find Developer Disk Image”. You probably gave up thinking that you need to update to Xcode 8 to be able to debug your app using an iOS 10 device. Good news is that you can still use Xcode 7 to debug your app with iOS 10 device! Here’s how.
 

Steps to Run app on iOS 10 device with Xcode 7

1. Download and install Xcode 8, but  do not delete or upgrade your Xcode 7 installation.
   You can download Xcode 8 XIP file here: https://developer.apple.com/download/more/
2. Create a symbolic link for Xcode 8 Developer Disk Image 10.0 in Xcode 7.
   You can open terminal then paste and run the following command. In this case, Xcode 8 is Xcode8.app while Xcode 7 is Xcode.app. Be sure to change to your actual Xcode paths.
   
   Swift

   ln -s /Applications/Xcode8.app/Contents/Developer/Platforms/iPhone‌OS.platform/DeviceSu‌pport/10.0\ \(14A345\) /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneO‌S.platform/DeviceSup‌port/

   1	ln -s /Applications/Xcode8.app/Contents/Developer/Platforms/iPhone‌OS.platform/DeviceSu‌pport/10.0\ \(14A345\) /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneO‌S.platform/DeviceSup‌port/

3. If your Xcode 7 is already open, restart Xcode 7 first.
4. Try to run your app on your iOS 10 device.

That’s it!
Happy debugging!

Reference:
http://stackoverflow.com/questions/39576363/could-not-find-developer-disk-image-ios-10