The operation couldn’t be completed. (Cocoa error 4.)

Have you checked that the path exists? also there is an // in the file path. Try to remove that one.

Could you also post you code, with out code we really have to guess.

The

Cocoa
error 4

means that you are trying to move a file that does not exist, this could also mean that the target directory does not exists.

查看路径是不是存在