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

I thought I would add my solution here too, in hopes to help someone. I just upgraded to Mac OS Mojave and I also upgraded to Xcode 10.2. My whole react native project broke, real bad. So then I downgraded Xcode back to 10.1. Then, I started to see this error, in said after running react-native run-ios:

Could not find iPhone X simulator

the above "hack" fixed it by editing the findMatchingSimulator.js file with the updates above.

Then, react-native run-ios got farther, next error was:

:CFBundleIdentifier, does not exist

I fixed this by:

1. cd node_modules/react-native/third-party/glog* TabEnter
2. ./configure

Now react-native run-ios works . I hope this helps someone, this was a pain in the @ss.

This bug has been fixed since RN v0.58.0, see commits here

IIRC this bug was introduced in Xcode 10.1

Also, you can fix this by simply replacing startsWith() with includes(). But doing this every time you update node_modules is less than ideal so I would recommend updating your RN version if possible.