I started learning react native. After installing all the things which are required for running react-native.

1. Update xCode to latest version. Or Install if not installed.
2. brew install watchman
3. npm install -g react-native-cli
4. react-native init HelloWorld
5. cd HelloWorld
6. react-native run-ios

Then I created a simple app called HelloWorld But after running the command

react-native run-ios

I received following error on the terminal
Could not parse the simulator list output

I already updated xcode to latest version. So I was not sure why this is happening. After doing some research I found that as I updated xcode to latest version I never started that. As it requires to install components after update.

So just open xCode and it will install all the components. And then run your program. Your problem will be solved.