Environment

React Native Environment Info:
System:
OS: macOS 10.14.2
CPU: (12) x64 Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz
Memory: 6.76 GB / 32.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.15.0 - /usr/local/bin/node
Yarn: 1.13.0 - /usr/local/bin/yarn
npm: 6.4.1 - /usr/local/bin/npm
SDKs:
iOS SDK:
Platforms: iOS 12.1, macOS 10.14, tvOS 12.1, watchOS 5.1
IDEs:
Android Studio: 3.1 AI-173.4819257
Xcode: 10.1/10B61 - /usr/bin/xcodebuild
npmPackages:
react: 16.6.3 => 16.6.3
react-native: 0.57.8 => 0.57.8
npmGlobalPackages:
create-react-native-app: 1.0.0
react-native-cli: 2.0.1
react-native-git-upgrade: 0.2.7

Description

I have been facing an issue where 'react-native run-ios' can not start, regardless of the simulator I add to the --simulator argument.
XCode has the correct location for the 'command line tools'

I am always getting the error:
Could not find iPhone X simulator

Error: Could not find iPhone X simulator
    at resolve (/Users/eric/.../swim/node_modules/react-native/local-cli/runIOS/runIOS.js:149:13)
    at new Promise (<anonymous>)
    at runOnSimulator (/Users/eric/.../swim/node_modules/react-native/local-cli/runIOS/runIOS.js:134:10)
    at Object.runIOS [as func] (/Users/eric/.../swim/node_modules/react-native/local-cli/runIOS/runIOS.js:106:12)
    at Promise.resolve.then (/Users/eric/.../swim/node_modules/react-native/local-cli/cliEntry.js:117:22)

Reproducible Demo

Installed XCode from scratch.
Brand new 'react-native new app'

'react-native run-ios' always complain about not finding the simulator, regardless of the --simulator option.

My temporary fix is to change:
/node_modules/react-native/local-cli/runIOS/findMatchingSimulator.js

line 42, to:
if (!version.startsWith('**com.apple.CoreSimulator.SimRuntime.**iOS') && !version.startsWith('tvOS')) {