How to implement a similar C # event mechanism in Lua

LuaIs similarC # eventsThe Mechanism learning tutorial is the content to be introduced in this article, mainly to learnEventInLuaFor more information, see.LuaThe syntax of metamethod is very flexible. It can be used to simulate the features of many languages.

C #We use the event as follows:

 
 

  
  
xxx.Click += new System.EventHandler(xxx_Click);  
  
  
 
  
  
private void xxx_Click(object sender, EventArgs e)  
  
  
{  
  
  
    /**/  
  
  
} 
 
 

To achieve the same effect in Lua and support event multicast mechanism, the key is to rewrite metamethod _ call so that not only functions can be called, but also tables can be called.

The main idea is to use a table to save several response functions for event registration, and then use the table as the function to call it. After rewriting _ call, implement traversal and execution of the Registration Method in the table when calling the table.

It needs to be executed on lua5.0 or lua.net, and lua 5.1 is slightly changed.

 
 

  
  
test.lua  
  
  
do 
 
 

Event prototype object. All events are generated by this prototype.

 
 

  
  
Event = {}
  
  
 
  
  
Function Event: New ()
  
  
Local event = {}
  
  
Setretriable (event, self)
  
  
-- Overwrite _ index Logic
  
  
Selfself. _ index = self
  
  
-- Overwrite _ call logic
  
  
Selfself. _ call = self. Call
  
  
Return event
  
  
End
 
 

Event registration: registers the response method to the event.

@ Source: the object to which the response method belongs

@ Func: Response Method

 
 

  
  
function Event:Add(source, func)  
  
  
    table.insert(self, {source, func})      
  
  
end 
 
 

Internal method. The default _ call logic is rewritten. When an event is triggered, the response method registered in the event is cyclically executed.

@ Table: when an object is called, it is passed in.

@: Call Parameters

 
 

  
  
Function Event. Call (table ,)
  
  
For _, item in ipairs (table) do
  
  
-- Item [1] is the source, item [2] is the func RESPONSE METHOD
  
  
-- Unpack (arg) is not required in lua 5.1 and can be directly used.
  
  
Item [2] (item [1], unpack (arg ))
  
  
End
  
  
End
 
 

The following are test cases:

Create a window object and register the Click Event of the button

 
 

  
  
Window = {  
  
  
    Name = "Simonw's Window",      
  
  
}  
  
  
function Window:Init() 
 
 

Register the event. self is the Window object source.

 
 

  
  
Button.ClickEvent:Add(self, self.Button_OnClick)      
  
  
 
 
 

Event Response Method. sender is the passed Button object.

 
 

  
  
function Window:Button_OnClick(sender)      
  
  
    print(sender.Name.." Click On "..self.Name)  
  
  
end 
 
 

Create a button object with events such as ClickEvent

 
 

  
  
Button = {
  
  
Name = "A Button ",
  
  
-- Create an event
  
  
ClickEvent = Event: New (),
  
  
}
 
 

Execute the button action

 
 

  
  
Function Button: Click ()
  
  
Print ('click begin ')
  
  
-- Trigger the event. self is the sender parameter.
  
  
Self. ClickEvent (self)
  
  
Print ('click end ')
  
  
End
 
 

Execute from here

 
 

  
  
Window:Init()  
  
  
Button:Click()  
  
  
--[[ 
 
 

Execution result:

 
 

  
  
> dofile 'test.lua'  
  
  
Click begin  
  
  
A Button Click On Simonw's Window  
  
  
Click end  
  
  
]]  
  
  
 
  
  
end 
 
 

Summary: AnalysisLuaIs similarC # eventsThe content of the Mechanism learning tutorial is complete. I hope this article will help you!