在真机运行程序的时候提示“Could not launch 'app name'”，No such file or directory (/Users/apple/Library/Developer/Xcode/DerivedData/mytest-ejkagqxooxgmtdfsdoygtyzflibe/Build/Products/Debug-iphoneos/mytest.app/mytest)
解决方法：先退出xcode，再把/Users/apple/Library/Developer/Xcode/DerivedData/下面的东西都删除（DerivedData本身不要删），再启动xcode，再rebuild.