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Anonymous Functions

Anonymous Functions

Jul 02 2018, 4:10 PM PST 2 min

An anonymous function is a function literal that has no direct identifier. They are used in shortening code. A downside to these functions are that you can only use them in the expression they’re formed in.

Examples

An anonymous function used with the DataType/RBXScriptSignal Connect function.

local brick = script.Parent
brick.Touched:Connect(function (part)
	--I'm a comment in an anonymous function!
	print("Beep")
end)

The above code is shorter than defining a named function, like such:

local brick = script.Parent

local function onTouch(part)
	--I'm a comment in a named function!
	print("Beep")
end

brick.Touched:connect(onTouch)

Closures

Anonymous functions are most commonly used in chat scripts or compound event scripts. These are used so that the arguments from the current function are still accessible.

Example

game.Players.PlayerAdded:connect(function(player)
	player.Chatted:connect(function (msg)
	--if this anonymous function was instead a named function outside of the anonymous function in the PlayerAdded connection,
	--it would not be able to access the `player` variable
	end)
end)

If you wanted to have the function in the Chatted connection to have a name, you would still have to use an anonymous function. It wouldn’t need to be nearly as long as the actual message-processing code though:

function onPlayerChatted(player, msg)
--thanks to the anonymous function below, this function has a **player** argument
end

game.Players.PlayerAdded:connect(function (player)
	player.Chatted:connect(function(msg)
	--message processing is in the onPlayerChatted function instead of here
		onPlayerChatted(player, msg)
		--this function is defined much faster than the possible long message processing code
	end)
end)

This is useful for shortening code, however this should be avoided in code that runs more than once. This is because the function is being defined more than once, which is unneeded because it is a literal function that is unchanging. These functions should be semantically named and used as such.

Tags:
  • coding
  • concept
  • lua