最近原来的老项目有点问题需要处理一下，运行启动命令，就报了如下错误，提示找不到iPhone 6 模拟器。
react-native run-ios Owaiss-Mac:pdm owaisahmed$ react-native run-ios Found Xcode project pdm.xcodeproj Could not find iPhone 6 simulator Error: Could not find iPhone 6 simulator at resolve (/Users/fantuan/Documents/react-native-projects/pdm/node_modules/react-native/local-cli/runIOS/runIOS.js:149:13) at new Promise (<anonymous>) at runOnSimulator (/Users/fantuan/Documents/react-native-projects/pdm/node_modules/react-native/local-cli/runIOS/runIOS.js:134:10) at Object.runIOS [as func] (/Users/fantuan/Documents/react-native-projects/pdm/node_modules/react-native/local-cli/runIOS/runIOS.js:106:12) at Promise.resolve.then (/Users/fantuan/Documents/react-native-projects/pdm/node_modules/react-native/local-cli/cliEntry.js:117:22)
老项目是一年前的当时项目的的版本时还是0.57，期间工作电脑的系统版本升级到了10.14.6， XCode的版本也升级到了10.3，使用如下命令可以查看当前项目的具体环境信息：
React Native Environment Info: System: OS: macOS 10.14.6 CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz Memory: 26.40 MB / 16.00 GB Shell: 5.3 - /bin/zsh Binaries: Node: 10.14.1 - ~/.nvm/versions/node/v10.14.1/bin/node Yarn: 1.13.0 - ~/.nvm/versions/node/v10.14.1/bin/yarn npm: 6.4.1 - ~/.nvm/versions/node/v10.14.1/bin/npm Watchman: 4.9.0 - /usr/local/bin/watchman SDKs: iOS SDK: Platforms: iOS 12.4, macOS 10.14, tvOS 12.4, watchOS 5.3 Android SDK: API Levels: 23, 25, 26, 27, 28, 29 Build Tools: 23.0.1, 23.0.3, 25.0.2, 25.0.3, 26.0.3, 27.0.3, 28.0.0, 28.0.2, 28.0.3, 29.0.2 System Images: android-23 | Intel x86 Atom, android-23 | Intel x86 Atom_64, android-23 | Google APIs Intel x86 Atom_64, android-29 | Google APIs Intel x86 Atom IDEs: Android Studio: 3.1 AI-173.4720617 Xcode: 10.3/10G8 - /usr/bin/xcodebuild npmPackages: react: 16.5.0 => 16.5.0 react-native: 0.57.0 => 0.57.0 npmGlobalPackages: react-native-cli: 2.0.1 react-native-create-library: 3.1.2
经过一番查阅资料发现是Xcode的版本升级到10导致的。
解决方案如下：
1.打开项目node_modules/react-native/local-cli/runIOS/findMatchingSimulator.js文件
2.修改文件的第31行
if (!version.startsWith('iOS') && !version.startsWith('tvOS')) { continue; }
为如下代码
if (!version.startsWith('com.apple.CoreSimulator.SimRuntime.iOS') && !version.startsWith('com.apple.CoreSimulator.SimRuntime.tvOS')) { continue; }
吐血注意：
对于ReactNative项目开发中，请不要轻易升级Xcode等编译，除非你十分精通。
