Xcode升级10.3后XiB文件包错，提示：

Failed to find or create execution context for description '<IBCocoaTouchPlatformToolDescription: 0x7fefbefd1d80> System content for IBCocoaTouchFramework-EightAndLater <IBScaleFactorDeviceTypeDescription: 0x7fefbebf4f70> scaleFactor=2x'. These intermediate objects were non-nil: (

一句终端命令解决问题

sudo killall - com.apple.CoreSimulator.CoreSimulatorService