报错信息：
/Users/zhaiyulei/Git/yxt/yxt/yxt/Supporting Files/Base.lproj/LaunchScreen.storyboard:-1: Failed to find or create execution context for description '<IBCocoaTouchPlatformToolDescription: 0x7fd8828999b0> System content for IBCocoaTouchFramework-EightAndLater <IBScaleFactorDeviceTypeDescription: 0x7fd8828b3440> scaleFactor=2x'. These intermediate objects were non-nil: (
这个是启动页的报错，在解决这个以后其他的XIB也会报错，所以这是一个全局的错误信息。
解决：
$ sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService$ sudo xcode-select -s /Applications/Xcode.app/Contents/Developer$ xcrun simctl erase all