(Original) cocos2d-x 3.0 + Lua learning and working (4): common functions (4): Handler

The functions here are mainly used for callback functions. Reference: quick_cocos.

 

Xingyue's contribution ~~~

 

--[[-- 将lua对象及方法包装为一个匿名函数-- 许多功能需要传入一个 Lua 函数做参数，然后在特定事件发生时就会调用传入的函数。例如触摸事件、帧事件等等。-- example：    local MyScene = class( "MyScene", function() )        return cc.Layer:create()    end )    function MyScene:ctor()        self.frameTimeCount = 0        -- 注册帧事件        self:addEventListener( cc.ENTER_FRAME_EVENT, self.onEnterFrame )    end        function MyScene:onEnterFrame( dt )        self.frameTimeCout = self.frameTimeCount + dt    end             上述代码执行时将出错，报告"Invalid self" ，这就是因为 C++ 无法识别 Lua 对象方法。         因此在调用我们传入的 self.onEnterFrame 方法时没有提供正确的参数。         要让上述的代码正常工作，就需要使用 handler() 进行一下包装：        function MyScene:ctor()        self.frameTimeCount = 0        -- 注册帧事件        self:addEventListener( cc.ENTER_FRAME_EVENT        , handler( self, self.onEnterFrame ) )    end             实际上，除了 C++ 回调 Lua 函数之外，在其他所有需要回调的地方都可以使用 handler()。-- @param obj lua对象-- @param function method 对象方法-- @return function--]]function handler( obj, method )    return function(...)        return method( obj, ... )    endend

A Simple Chat ~ (Xiao Bai: chatting about wool. You think everyone is free to talk about it like you ...)

function handler( obj, method )    return function(...)        return method( obj, ... )    endendlocal Music = {}function Music:test( str )    print( "Music: " .. str )endlocal t = handler( Music, Music.test )t( "小白：星月是帅哥；星月：小白就是坦诚~~~" )输出：Music: 小白：星月是帅哥；星月：小白就是坦诚~~~

 

Handler returns a function, which is assigned to T. When the function T is called, the Music method test (STR) is called, so the above output is displayed.

What is the principle of T function call? (Xiao Bai: No one forces you to say it ~~~)

t( "小白：星月是帅哥；星月：小白就是坦诚~~~" )展开后就是：method( obj, "小白：星月是帅哥；星月：小白就是坦诚~~~" )method就是：Music.test。obj就是：Music。所以，替换后就是：Music.test( Music, "小白：星月是帅哥；星月：小白就是坦诚~~~" )Music找到函数test，因为用的是 “.” 点号调用函数，所以第一个参数就是self，第二个参数才是test方法里面的str。

Everyone understands it (Xiao Bai: No ~~~)
The content of this chapter ends here and I hope it will be useful to you ~

(TOM: Wait. I haven't figured it out ...)

 

The author uses cocos2d-x 3.0 + Lua learning and work experience, without the author's consent, please do not reprint! Thank you for your patience ~~~

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Address: http://www.cnblogs.com/wodehao0808/p/4017210.html

(Original) cocos2d-x 3.0 + Lua learning and working (4): common functions (4): Handler