Event

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Class reference

An Event is a special kind of Roblox Object. It provides a way for user-defined functions to be called when something happens in the Game.

Functions

Events have these functions:

• connect(Function callback)
• wait()
• disconnect(Function callback)

connect

The connect method establishes a function to be called whenever the event occurs. The function is called with the arguments for that event. The connect method returns another special object called a connection object.

Example

game.Workspace.Part.Touched:connect(myTouchedFunction)

This causes myTouchedFunction to be called whenever that Part is touched by another Part.

wait

Works like the global wait function except that instead of waiting for a fixed period of time, it waits for the next occurance of the Event. The return value is arguments of the event.

Example

local otherPart = Workspace.Part.Touched:wait()

This causes the script to stop and wait for that Part to be touched by another Part.

deprecated: disconnect

The old method of using Event:disconnect method is superceded by Connection:disconnect.

Usage

Take the example of the Touched event of Part:

Touched ( BasePart otherPart )
Description	Fired when another object comes in contact with this object.
Member of:	BasePart

The first section tells you there's an event named "Touched" which has arguments "Instance otherPart". The middle section explains when the event will occur and why. The last section lists types of objects that have this event.

We use this information to create a function and a "connection" line in our script.

Traditionally, such functions are called "handlers" and are named on{Event Name}:

function onTouched()

The arguments that will be passed by the event are given by "Instance otherPart". This means that "otherPart" will be passed and the type will be Instance (which all Parts are).

To allow our function to use that, we defined it as:

function onTouched(otherPart)

Finally, we can used the last piece of information to make a connection to that function:

part.Touched:connect(onTouched)

Example

local part = game.Workspace.Part -- your part here
function onTouched(otherPart)
  otherPart.Transparency = 1 -- make part that touched invisible
  part.BrickColor = BrickColor.Random() -- give this part a new random color
end

part.Touched:connect(onTouched) -- call onTouched each time something touches

Here we are giving "otherPart" to the function. This allows us to use the variable "otherPart" inside the function to be our part that we set up above, in the variable "part".

Limitations

Connections are also automatically removed if:

• The called function generates an error before the first wait() call.
• The script itself is removed or reparented.

Note: The connect method does not check that the argument is a valid function. If you misspell the name or otherwise give an invalid function you'll get an error when the event next triggers:

Fri Apr 23 21:50:48 2010 - attempt to call a nil value
Fri Apr 23 21:50:48 2010 - 

Notice that the error has no script reference or line number. This is because it comes from Roblox itself inside the Event generation code.

Advanced Usage

Any function name is valid:

function blah()
  print("In event")
end
part.Changed:connect(blah)

Using anonymous functions in connect is common:

part.Touched:connect( 
function(otherPart)
  otherPart.Transparency = 1
  part.BrickColor = BrickColor.Random()
end) -- end anonymous function and connect

You can also use anonymous functions to change the arguments:

player.Chatted:connect(
function(message, recipient)
  onChatted(player, message) -- new arguments need to match onChatted function call
end)

You can create connections at any time even inside of event functions:

function onChatted(player, message)
  print(player .. " said " .. message)
end

function onPlayerAdded(player)
  player.Chatted:connect(function(message, recipient) onChatted(player, message) end)
end

Game.Players.PlayerAdded:connect(onPlayerAdded)

connection

The connection object is a special object returned by the connect() method of an Event.

Functions

It has 1 method:

• disconnect()

disconnect

The connection object disconnect method, removes the association created by connect. The defined function will no longer be called when the Event occurs.

Example

-- turn on connection
local conn = part.Touched:connect(onTouched)

-- later to turn off connection
conn:disconnect()