How to add modifier to user defined command?

Question

I'd like to write commands that work with :tab and :vert. Say I have a command that opens a new split window as shown below

function! FooSplit()
    let l:message="hello world"
    new
    put! =l:message
endfunction
command! -complete=command Foo call FooSplit()

I'd like it to make it so that :tab Foo and :vert Foo will open in a new tab and vertical split respectively.

Answer 1

You can use :h <mods> to do this, it expands to modifier or nothing. It's added at patch 7.4.1898

command Foo call FooSplit(<q-mods>)

function FooSplit(mods)
  exe a:mods 'new'
endfunction

Above example use <q-mods> instead of <mods>, as you need it as a string.