Vim: How to synchronize NERDTree with current opened tab file path?

I use the following mapping to view the current buffer in NERDTree:

 map <leader>r :NERDTreeFind<cr>

throw a % sign on the end like a boss

:NERDTree %

i have this in my .vimrc, it maps Ctrl+o to toggle nerdtree in the dir of the current buffer:

map <C-o> :NERDTreeToggle %<CR>

I found both the existing answers educational, and successfully combined the two so that the behavior is more like many people would expect from an IDE: Click on an open window/buffer, and have that file highlighted in the NERDTree. I put this in my ~/.vimrc:

autocmd BufEnter * if &modifiable | NERDTreeFind | wincmd p | endif

What this does:

1. autocmd BufEnter - runs every time you focus on a buffer (including the NERDTree window)
2. if &modifiable - when you do click the NERDTree window, do nothing else (the NERDTree window is not modifiable)
3. wincmd p - NERDTreeFind leaves the cursor focused on the NERDTree; this switches back to the window you'd originally focused on

Note that this won't work on any other buffer that isn't modifiable -- but that's generally a good thing; otherwise (for example) any time you got :help in vim, NERDTree would find and focus the directory where help files are stored--probably not something you want it to do.

That one-line solution worked great for me at first, but I soon found that it causes NERDTree to activate any time I opened a file--and as a result, it prevents NERDTree from ever being closed! If you don't want to use NERDTree full-time, put this in your .vimrc instead:

" returns true iff is NERDTree open/active
function! rc:isNTOpen()        
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

" calls NERDTreeFind iff NERDTree is active, current window contains a modifiable file, and we're not in vimdiff
function! rc:syncTree()
  if &modifiable && rc:isNTOpen() && strlen(expand('%')) > 0 && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

autocmd BufEnter * call rc:syncTree()