Since upgrading to Xcode 10.2 I can no longer run react-native run-ios through the cli
I solved like this ;
Firstly, you need to go this path
node_modules/react-native/local-cli/runIOS/findMatchingSimulator.js
and then;
You need to change this code
if (!version.startsWith('iOS') && !version.startsWith('tvOS'))
with
if (!version.startsWith('com.apple.CoreSimulator.SimRuntime.iOS') && !version.startsWith('com.apple.CoreSimulator.SimRuntime.tvOS'))
I hope, it will be helpful,
ref : https://github.com/facebook/react-native/issues/21498#issuecomment-476621627