Releasing connection in connectionDidFinishLoading cause bad instruction

According to URL Loading System Programming Guide NSConnection sample code I can release connection in connectionDidFailWithError and connectionDidFinishLoading.

However, releasing connection in conn开发者_高级运维ectionDidFinishLoading causing

objc[19685]: FREED(id): message releaseDelegate sent to freed object=0x3b41630
Program received signal:  “EXC_BAD_INSTRUCTION”.

Why?

If you doesn't retain the object you receive from [NSConnection connectionWithRequest:] then you must not call release on it.

This is a double release error. It means either you didn't retain an object enough times, or you sent it too many release messages.