This application failed to start because it could not find or load the Qt platform plugin “cocoa”

Question

I think I did everything I could in the last 20 hours, but nothing seems to work. My app is running and working -- just as it should -- the only problem I have is that I can

Answer 1

This is in addition to @mfitzp's answer.

This QT Plugins Document came in handy.

To look for default locations that your QT app is trying to search you can use following command:

$sudo dtruss MacOS/ncher 
  getattrlist("/ncher.app\0", 0x7FFF954B51A4, 0x7FFF5C8FDD20)              = 0 0
  getattrlist("/ncher.app/Contents\0", 0x7FFF954B51A4, 0x7FFF5C8FDD20)             = 0 0
  getattrlist("/ncher.app/Contents/MacOS\0", 0x7FFF954B51A4, 0x7FFF5C8FDD20)               = 0 0
  stat64("/ncher.app/Contents/MacOS\0", 0x7FFF5C8FDED8, 0x7FFF5C8FDD20)            = 0 0
  stat64("/ncher.app/Contents/MacOS/platforms/.\0", 0x7FFF5C8FDF58, 0x7FFF5C8FDD20)                = -1 Err#2
  open("/dev/tty\0", 0x1000000, 0x1FF)             = 5 0
  fcntl(0x5, 0x2, 0x1)             = 0 0
  close(0x5)               = 0 0
  write_nocancel(0x2, "This application failed to start because it could not find or load the Qt platform plugin \"cocoa\".\n\nReinstalling the application may fix this problem.\n\0", 0x97)              = 151 0
  sigprocmask(0x3, 0x7FFF5C8FE6B4, 0x0)            = 0x0 0
  __pthread_sigmask(0x3, 0x7FFF5C8FE6C0, 0x0)              = 0 0
  __pthread_kill(0x603, 0x6, 0x0)          = 0 0
  kevent64(0x4, 0x0, 0x0)          = -1 Err#4

You can see this QT app trying to look into MacOS/platforms, once i copied my libqcocoa.dylib plugin (its path were modified by install_name_tool command as per @mfitzp's answer) there, my application worked like charm.

BTW it is advisable by MAC codesigning guide to have this directory structure correctly setup,

DONT put Frameworks, plugins in ncher.app/Contents/MacOS directory