Error Running React Native App From Terminal (iOS)

Check out this link (Running react-native run-ios occurs an error?). It appears to be a problem with the location of Command line tools.

In Xcode, select Xcode menu, then Preferences, then Locations tab. Select your Xcode version from the dropdown and exit Xcode.

XCode location tab

You may need to install or set the location of the Xcode Command Line Tools.

Via command line

If you have Xcode downloaded you can run the following to set the path:

sudo xcode-select -s /Applications/Xcode.app

If the command line tools haven't been installed yet, you may need to run this first:

xcode-select --install

You may need to accept the Xcode license before installing command line tools:

sudo xcodebuild -license accept

Or adjust the Command Line Tools setting via Xcode (Xcode > Preferences > Locations):

Xcode preferences - Locations tab