Server.is_installed() -> attempt to index local 'self' a nil value

[sethidden]

Hey, I've been trying to create a simple "ensure those servers are installed everytime nvim is launched" function and I came up with this:

local nvim_lsp_installer = require('nvim-lsp-installer')
local lspinstaller_ensure_installed = function()
  local servers = {'jsonls', 'sumneko_lua', 'eslint', 'pyright', 'omnisharp'}
  for _, name in pairs(servers) do
    local ok, server = nvim_lsp_installer.get_server(name)
    print(server.name, ok)
    print(server.is_installed)
    print(server.is_installed()) -- fails here
    if ok and not server.is_installed() then
      server.install()
    end
  end
end
lspinstaller_ensure_installed()

But on the

print(server.is_installed()) -- fails here

line I get the following output+error:

jsonls true                                                                                                                                                                                      
function: 0x7ff2488c6958                                                                                                                                                                         
Error detected while processing /home/artur/.dotfiles/.config/nvim/plugin/lsp.lua:                                                                                                               
E5113: Error while calling lua chunk: ...art/nvim-lsp-installer/lua/nvim-lsp-installer/server.lua:123: attempt to index local 'self' (a nil value)                                               
stack traceback:                                                                                                                                                                                 
        ...art/nvim-lsp-installer/lua/nvim-lsp-installer/server.lua:123: in function 'is_installed'                                                                                              
        /home/artur//.config/nvim/./plugin/lsp.lua:85: in function 'lspinstaller_ensure_installed'                                                                                               
        /home/artur//.config/nvim/./plugin/lsp.lua:91: in main chunk

I suspect this is some stupid mistake on my part that I can't see, but I haven't been able to resolve it. Anybody know what's up?
My dotfiles, and the lsp part of the setup are here: https://github.com/sethidden/dotfiles/blob/cebce3ced28699152f8a06e3466c26c93e445895/.config/nvim/plugin/lsp.lua

[williamboman]

Hello! The server variable you're interacting with is an instance of a metatable (this is conceptually very similar to normal classes found in other languages). This metatable have different methods such as is_installed(), which all operate on an individual instance. Without going into too much detail - the problem is that you're not providing which instance the method should target.

On phone atm so I can't verify whether I'm 100% correct now, but the following should explain it in code:

-- You need to provide the server instance as an argument to the metatable (class) functions!
server.is_installed(server)
server2.is_installed(server2)

-- The above looks really awkward though, so there's some syntactic
-- sugar which does this for you (this is the conventional way of doing it)
server:is_installed() -- use a : instead of .
server2:is_installed()

-- Other examples
local my_str = "hello"
string.find(my_str, "something")
-- or
my_str:find("something")

Makes sense?

[sethidden]

Yep that did it :) Thanks for the help, especially on mobile :P Hope your fingers are fine