Lua实现事件派发器

为了降低模块间的耦合, 很多系统使用事件派发机制, 接收方无需知道派发者是谁.在Qt中,这个系统被称作Slot&Signal, 需要配合moc代码生成机制, 但是系统本身是线程安全的.

这里我们讨论的是lua的事件派发机制, 我将此写成lua模块, 方便配合cocos2dx进行逻辑处理

 

local Global = _G

local package = _G.package

local setmetatable = _G.setmetatable

local assert = _G.assert

local table = _G.table

local pairs = _G.pairs

local ipairs = _G.ipairs

module "Core.EventDispatcher"

--[[

数据层次

["EventName1"] =

{

    ["_StaticFunc"] = { Func1, Func2 },

    [Object1] = { Func1, Func2 },

    [Object2] = { Func1, Func2 },

},

["EventName2"] =

{

    ...

}

]]

-- 默认调用函数

local function PreInvoke( EventName, Func, Object, UserData, ... )

    if Object then

        Func( Object, EventName, ... )

    else

        Func( EventName, ... )

    end

end

function New( )    

    local NewObj = setmetatable( {}, { __index = package.loaded["Core.EventDispatcher"] } )

    -- 对象成员初始化

    NewObj.mPreInvokeFunc = PreInvoke

    NewObj.mEventTable = {}

    return NewObj

end

-- 添加

function Add( Self, EventName, Func, Object, UserData )

    assert( Func )

    Self.mEventTable[ EventName ] = Self.mEventTable[ EventName ] or {}

    local Event = Self.mEventTable[ EventName ]

    if not Object then

        Object = "_StaticFunc"

    end

    Event[Object] = Event[Object] or {}

    local ObjectEvent = Event[Object]

    ObjectEvent[Func] = UserData or true

end

-- 设置调用前回调

function SetDispatchHook( Self, HookFunc )

    Self.mPreInvokeFunc = HookFunc

end

-- 派发

function Dispatch( Self, EventName, ... )

    assert( EventName )

    local Event = Self.mEventTable[ EventName ]

    for Object,ObjectFunc in pairs( Event ) do

        if Object == "_StaticFunc" then

            for Func, UserData in pairs( ObjectFunc ) do

                Self.mPreInvokeFunc( EventName, Func, nil, UserData, ... )    

            end

        else

            for Func, UserData in pairs( ObjectFunc ) do

                Self.mPreInvokeFunc( EventName, Func, Object, UserData, ... )

            end

        end

    end

end

-- 回调是否存在

function Exist( Self, EventName )

    assert( EventName )

    local Event = Self.mEventTable[ EventName ]

    if not Event then

        return false

    end

    -- 需要遍历下map, 可能有事件名存在, 但是没有任何回调的

    for Object,ObjectFunc in pairs( Event ) do

        for Func, _ in pairs( ObjectFunc ) do

            -- 居然有一个

            return true

        end

    end

    return false

end

-- 清除

function Remove( Self, EventName, Func, Object )

    assert( Func )

    local Event = Self.mEventTable[ EventName ]

    if not Event then

        return

    end

    if not Object then

        Object = "_StaticFunc"

    end

    local ObjectEvent = Event[Object]

    if not ObjectEvent then

        return

    end

    ObjectEvent[Func] = nil

end

-- 清除对象的所有回调

function RemoveObjectAllFunc( Self, EventName, Object )

    assert( Object )

    local Event = Self.mEventTable[ EventName ]

    if not Event then

        return

    end

    Event[Object] = nil

end

这里注意下, 我是将EventDispatcher.lua放置在Core目录下, 因此需要使用require “Core.EventDispatcher”进行调用

使用用例

 

    local EventDispatcher = require 'Core.EventDispatcher'

    local E = EventDispatcher.New()

    E:Add( "a", function( a, b )   print( a, b ) end )

    local Func = function( a )   print( a ) end 

    E:Add( "a", Func )

    E:Dispatch("a", 1, 2 )

    print( E:Exist("a"), E:Exist("b"))

    E:Remove("a", Func )

    E:Dispatch("a", 1, 2 )

    print( E:Exist("a"), E:Exist("b"))