You have probably used triggers if you are learning scripts and you may say “Script is so hard.” but in reality, it is really similar to triggers, there are functions that listen for events, what listening or Listeners are in programming, they are programs or specific functions within a program that waits for and responds to specific events or messages. In other words. It's a function that waits for an event and does something when that event happens.

That's why script and triggers are similar, because they both follow the structure

Event: Listener function

Condition: Conditionals, relational operators, logical operators, etc

Action: Executing the code

To use the events one must call the function in the script

 ScriptSupportEvent:registerEvent([=[EventName]=],FunctionToExecute) 

Where we change EventName to the name of the event that we would like to listen, you can find the event list in Script page on the Classes and the FunctionToExecute parameter is the function we would like to execute when that event happens (More info about functions Lua functions chapter)

The function will return a table with all the important information such as

• The id of the player or actor who triggered the event (eventobjid)
• The id of the player or actor directly affected by the event (toobjid) Not applicable to most events
• Parameters of the event

In this example when the player gets any buff the player who got the buff will send to chat “I got a buff!” for this, we can use the event Player.AddBuff that returns the eventobjid, the parameter buffid

We first define a function and make it so it takes args that were returned

function GetBuff(params)
end

and we take the listener function and replace EventName with our event which is Player.AddBuff

 ScriptSupportEvent:registerEvent([=[Player.AddBuff]=], FunctionToExecute) 

and we replace FunctionToExecute with our function's name which is GetBuff

ScriptSupportEvent:registerEvent([=[Player.AddBuff]=], GetBuff) 

The code should look something like this:

    function GetBuff(params) 
 
    end
 
    ScriptSupportEvent:registerEvent([=[Player.AddBuff]=], GetBuff)

But if we execute it right now it will do nothing, we need to add more functionality, and to make the player send a message to the chat we can use the Chat:sendChat(content, targetuin) method, it makes the player send a chat, the content argument is what we want the player to write, for this example we will use “I just got a buff” but you can change it to whatever you want, as long as its a string (More info about strings in Lua string page and the targetuin is the uid of the player that will send the message, but how do we get it?

The answer is that we need to use the function arguments variable name (in this case params) and we can retrieve them with params.paramname or params['paramname'] we know that Player.AddBuff gives us the eventobjid and buffid. We want the eventobjid so we retrieve it as params.eventobjid or params['eventobjid'].

The code now should look like this:

    function GetBuff(params) 
        Chat:sendChat("I just got a buff!", params.eventobjid)
    end
 
    ScriptSupportEvent:registerEvent([=[Player.AddBuff]=], GetBuff)

Now, if we execute it, our character should send a message when we get any buff!

That's great, but what if we want that when the player gets a specific buff the player send a message, and when the player gets another buff that is not the one that we want, we send another message, we can do it using the if and else conditional, we get the id of the buff we want using the id library, we get two ids when we select any buff, the first is the buffid and the second the bufflv but this is not important, so we add to our GetBuff function an if statement that checks if params.buffid == 40 (If the player got the buff with the id 40 then execute this code) and an else statement which sends our original message

    function GetBuff(params)
	if params.buffid == 40 then
            Chat:sendChat("I'm big now!", params.eventobjid)
	else
	    Chat:sendChat("I just got a buff!", params.eventobjid)
	end
    end

Now, when we execute the game and get any buff we will get the original message, but if we get the buff we want, we will send “I'm big now!”, now, you may ask if there's a more efficient way to get the params, and the answer is YES! We can declare a variable and then use it, the code would look like this and work the same, but we can use the variable name instead of the “params.paramname” or “params['paramname']

Code:

    function GetBuff(params)
        local curid = params.buffid
        local playerid = params.eventobjid
 
	    if CurId == 40 then
        	Chat:sendChat("I'm big now!", playerid)
	    else
		    Chat:sendChat("I just got a buff!", playerid)
	    end
    end