What does the pipeline character do in functions (LUA)

[MisterGrinch2017]

local function get_player(name: string): Player | nil
    name = name:lower()
    --...
end

I have this dummy function (literally just from a piece of code I saw).

What does the (name: string): Player | nil do? I know that ‘name’ is the parameter, ‘string’ is the parameter accepting type, but what is the colon ( : ) after string) for? And how does the pipeline character work?

Thanks ahead.

[kalabgs (FartFella)]

That’s just type checking
Since roblox is not statically typed language it does something similar to TS to have types.

its primarily for aesthetics

[weakroblox35]

it just returns what the function will return

function get_player(name: string?): Player?
    if game:GetService("Players"):FindFirstChild(string.lower(name) then
      return game:GetService("Players"):FindFirstChild(name) -- will return player.
    end
end

[MisterGrinch2017]

so when I’m typing out the function, I would see “Player?” on a ribbon near my cursor?

[weakroblox35]

Yes. Assuming the functions finds the player and returns it.

[MisterGrinch2017]

That’s nice! Thx for the link! It’s caused I never knew there was a use for the pipeline in LUA

[MisterGrinch2017]

Oh so it’s not just a description or custom text that works like reminders for devs?

[weakroblox35]

It’s typechecking, like descriptions.

[RickAstll3y]

This means that it expects the name to be a string
And it will either return a Player or nil

Player | nil is the same as Player?

[MisterGrinch2017]

thank you, but a little more detailed, does the ( | ) mean “or” in type checking?

[MisterGrinch2017]

thank you! =) characters characters

[gertkeno (Gert)]

Yes, the type returned by the function will be either a Player or nil.

To enable type checking on scripts put --!strict at the very top, line #1

[MisterGrinch2017]

I’m not going to mark a solution to a specific user, because all of ya’ll made big help. It’s not fair to give just one user the solution mark.