Stop Dropbox from synchronising Vim swap files

A workaround is to change the location of swap files with the directory option. For example, add the following to your .vimrc:
set directory=~/tmp//,.,/var/tmp//,/tmp// Note the trailing double slash which indicates that swap file names will include the full path, thus avoiding file name collisions.

Sources

• http://vim.wikia.com/wiki/Remove_swap_and_backup_files_from_your_working_directory