“Could not find iPhone X simulator” in react-native after Xcode 10.2 update

Could not find iPhone X simulator

react-native run-ios

Do the following to solve this

open ./node_modules/react-native/local-cli/runIOS/findMatchingSimulator.js

This is how this file will look

// Making sure the version of the simulator is an iOS or tvOS (Removes Apple Watch, etc)
    if (!version.startsWith('iOS') && !version.startsWith('tvOS')) {
      continue;
    }

Let's change it to

// Making sure the version of the simulator is an iOS or tvOS (Removes Apple Watch, etc)
   /*
    if (!version.startsWith('iOS') && !version.startsWith('tvOS')) {
      continue;
    }*/
    if (!version.startsWith('com.apple.CoreSimulator.SimRuntime.iOS') && !version.startsWith('com.apple.CoreSimulator.SimRuntime.tvOS')) {
      continue;
    }

and then run react-native run-ios.

Solved !!