error: failed to attach to process ID 丫的，史上最经典的错误啊~ google国内的文档就丫几篇，还都是提问的。国外牛人不少，特搜一篇，如有同报错者，可得矣~Open only XCode without opening project -> Go to Window -> Organizer -> [ProjectName] and delete it completely -> Quit XCode -> Open iPhone simulator and reset settings -> Quit iPhone simulator -> reboot Mac -> reopen XCode and run application