Using Callbacks in Code
Using Callbacks in Code
Callbacks are write-only members of objects that are set to functions. You cannot invoke a callback directly — Roblox will internally trigger the callback function, and pass to it relevant information your callback handler/function will need.
DataModel/OnClose, which fires before the game shuts down and gives scripts a chance to save data
MarketplaceService/ProcessReceipt, which is used to handle developer products purchases
RemoteFunction/OnClientInvokewhich is invoked when the server calls RemoteFunction:FireClient(player, …) or RemoteFunction:FireAllClients(…).
RemoteFunction/OnServerInvokewhich is invoked when a client calls RemoteFunction:InvokeServer(…)
BindableFunction/OnInvokewhich is invoked when a script calls BindableFunction:Invoke(…)
To set a callback, you assign it to a function:
local bindableFunction = Instance.new("BindableFunction") bindableFunction.OnInvoke = function() return 1337 end
Callbacks are write-only, meaning you cannot get the value of a callback.
local bindableFunction = Instance.new("BindableFunction") print(bindableFunction.OnInvoke)
OnInvoke is a callback member of BindableFunction; you can only set the callback value, get is not available
To invoke the callback, in this case, you’ll use BindableFunction:Invoke(). All of the arguments you pass to :Invoke() will be passed to the callback function, and then the return value from the callback function will be returned to the caller of :Invoke().
local bindableFunction = Instance.new("BindableFunction") bindableFunction.OnInvoke = function(n) return 2 * n end print(bindableFunction:Invoke(42))
Suppose you want to make a BindableFunction and bind it to a function that receives two arguments, let’s say, the Name of a part and its Size, and that creates a Part, puts it in the Workspace, and gives it the Name and the Size passed to the function.
You would first create the BindableFunction:
local func = Instance.new("BindableFunction", script.Parent)
And you would then connect it to your function, using the OnInvoke callback:
local func = Instance.new("BindableFunction", script.Parent) func.OnInvoke = function(name, size) local part = Instance.new(**Part**) part.Name = name part.Size = size part.Parent = workspace end
Now, you can just call the BindableFunction like this, and it will create the part:
BindableFunction:Invoke("Brick", Vector3.new(50, 50, 50))