升级 Xcode 10.2 之后无法使用 react-native run-ios ，报错如下：

Found Xcode workspace a.xcworkspace

Could not find iPhone X simulator

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

解决方法：
找到 /项目地址/node_modules/react-native/local-cli/runIOS/findMatchingSimulator.js

搜索下面这行代码

if (!version.startsWith('iOS') && !version.startsWith('tvOS'))

改为

 if (!version.startsWith('com.apple.CoreSimulator.SimRuntime.iOS') && !version.startsWith('com.apple.CoreSimulator.SimRuntime.tvOS'))

现在试试 react-native run-ios 应该好了……