" vice.vim needs to know the SID of where the methods are defined.
function! s:SID()
    return matchstr(expand('<sfile>'), '<SNR>\zs\d\+\ze_SID$')
endfunction

" 'generate_stub' is defaultly 0 for some reasons.
" you can omit the vice#class()'s 3rd argument
" if you like default one.
let s:VICE_OPTIONS = {'generate_stub': 1}


" Trait

let s:Printable = vice#trait('Printable', s:SID(), s:VICE_OPTIONS)

function! {s:Printable.method('print')}(self)
    echon a:self.message()
endfunction

function! {s:Printable.method('say')}(self)
    echo a:self.message()
endfunction

function! s:Printable.requires()
    return ['message']
endfunction


let s:Foo = vice#class('Foo', s:SID(), s:VICE_OPTIONS)
call s:Foo.with(s:Printable)

function! {s:Foo.method('message')}(self)
    return 'foo'
endfunction


let s:Bar = vice#class('Bar', s:SID(), s:VICE_OPTIONS)
call s:Bar.with(s:Printable)

function! {s:Bar.method('message')}(self)
    return 'bar'
endfunction


echon "--- Foo ---\n"

let foo = s:Foo.new()
" "foo"
call foo.print()
" "foo" with newline
call foo.say()

echon "\n"
echon "--- Bar ---\n"

let bar = s:Bar.new()
" "bar"
call bar.print()
" "bar" with newline
call bar.say()

let s:class = vice#new('Klass')
let meta = s:class._meta

" Create Pair type (local to s:buffer_string object).
function! meta.subtype('Pair', 'List').where(Value)
    return len(a:Value) == 2
endfunction

" Create Pair type (local to s:buffer_string object).
function! meta.subtype('Pair', 'List').define()
    function self.where(Value)
        return len(a:Value) == 2
    endfunction
endfunction