更新Xcode 10.2后React Native iOS编译及模拟器启动报错求助

Hey there, let's work through these two issues you're hitting with Xcode 10.2 and your React Native app. Both the compilation error and the simulator launch problem are likely tied to compatibility glitches or stale cached data from the Xcode update. Here's a step-by-step breakdown of what to try:

This error points to Interface Builder struggling to locate a valid iPad device type, which usually stems from outdated cache or mismatched simulator configurations.

• Clean Xcode's Build Cache and Derived Data
  Xcode often hangs onto old cached files after updates, which can break compatibility. Here's how to clear it out:

  • Open Xcode, navigate to Xcode > Preferences > Locations
  • Click the arrow next to the Derived Data path to open the folder in Finder, then delete the entire folder
  • Alternatively, run this command in Terminal to wipe it via command line:

    rm -rf ~/Library/Developer/Xcode/DerivedData
    

  • Back in Xcode, go to Product > Clean Build Folder (hold the Option key if you don't see this option initially)

• Reinstall the iOS 12.2 Simulator Runtime
  Sometimes the simulator runtime doesn't install correctly during Xcode updates. Let's verify and fix that:

  • Open Xcode, go to Xcode > Preferences > Components
  • Look for the iOS 12.2 Simulator entry. If it's not installed, click the download button. If it is installed, try removing it and reinstalling—fresh installs often fix corrupted runtime files.

• Update React Native Dependencies
  Older React Native versions might not play nice with Xcode 10.2. Try updating your core packages:

  • Run this to update React Native (you can specify a version known to work with Xcode 10.2, like 0.59.x or higher, if you don't want the latest):

    npm install react-native@latest --save
    

  • If you use CocoaPods for iOS dependencies, update those too:

    cd ios && pod install --repo-update
    

• Check Your Target Device Compatibility
  Xcode 10.2 drops support for devices that can't run iOS 12 (like the iPad 2, which maxes out at iOS 9). The error mentions iPdad2x (likely a typo for iPad 2), so double-check your project settings:

  • In Xcode, go to your project target's General > Deployment Info
  • Ensure the Device dropdown is set to a device compatible with iOS 12.2 (e.g., iPad Air, iPad Pro, etc.)—avoid deprecated devices like the iPad 2.

This issue is almost certainly linked to the same simulator configuration problems causing the compilation error. Try these fixes:

• Reset Simulator Content and Settings
  Corrupted simulator state can block launches. Here's how to reset it:

  • If you can get any simulator to open, go to Simulator > Reset Content and Settings... and confirm the reset
  • If you can't open the simulator at all, run this Terminal command to wipe all simulators:

    xcrun simctl erase all
    

• Restart Xcode and Your Mac
  It sounds simple, but a full restart can clear stuck background processes that are blocking the simulator. Close Xcode completely, kill any lingering "Simulator" or "com.apple.CoreSimulator" processes via Activity Monitor, then restart your Mac and try launching the simulator again.

• Restart the CoreSimulator Service
  The CoreSimulator service manages all simulator instances, and it can get stuck after updates:

  • Run these commands in Terminal to restart it:

    sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService
    xcrun simctl list
    

  If the xcrun simctl list command outputs a list of available simulators, that means the service is working correctly again.

内容的提问来源于stack exchange，提问作者lecham