Event: Difference between revisions
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local part = game.Workspace.Part -- your part here | local part = game.Workspace.Part -- your part here | ||
function onTouched(otherPart) | function onTouched(otherPart) | ||
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Here we are giving "otherPart" as an argument to the event handler, onTouched. | Here we are giving "otherPart" as an argument to the event handler, onTouched. | ||
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}} | }} | ||
Revision as of 16:00, 14 August 2011
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.
Methods
Events have these methods:
- connect(Function callback)
- connectFirst(Function callback)
- connectLast(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.
game.Workspace.Part.Touched:connect(myTouchedFunction)
This causes myTouchedFunction to be called whenever that Part is touched by another Part.
connectFirst
The connectFirst method acts like the connect method, except that the function provided gets called before any other function connected to that event.
connectLast
The connectLast method acts like the connect method, except that the function provided gets called after every other function connected to that event.
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 values are the event arguments.
local otherPart = Workspace.Part.Touched:wait()
This causes the script to stop and wait for that Part to be touched by another Part.
disconnect (deprecated)
The old method of using Event:disconnect method is superceded by Connection:disconnect.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 bind our function to that event:
part.Touched:connect(onTouched)
local part = game.Workspace.Part -- your part here function onTouched(otherPart) otherPart.Transparency = 1 -- make part that was 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" as an argument to the event handler, onTouched.
Limitations
Connections are also automatically removed if:
- The event handler 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` method call
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:
Properties
It has 1 property: