[CoronaSDK/Lua] Function Delegate2

FuncDelegate2.lua

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-- function delegate part 2
-- Author: Erin Lin
-- www.erinylin.com
-- 簡易模擬 C# delegate
-- licensed under the MIT license.
-- 2015, 03
-- 參考：https://gist.github.com/anonymous/3f0e5b046bfdcfa9864a
-------------------------------------

local next = next
local unpack = unpack
local t = {
    remove = table.remove,
    insert = table.insert,
    indexOf = function(list, value)
        local n = 0
        for k, v in next, list do
            if v==value then return k end
        end
        return -1
    end
}

local meta = {
     __add = function(x, y)
        if type(y) == "function" then
            t.insert(x, y)
            return x
        elseif type(y) == "table" then
            for i=1,#y do
                if type(y[i]) == "function" then t.insert( x, y[i] ) end
            end
            return x
        end
    end,
    __sub = function(x, y)
        if type(y) == "function" then
            local index = t.indexOf( x, y )
            if index > -1 then t.remove( x, index ) end
            return x
        elseif type(y) == "table" then
            for i=#y,1,-1 do
                local index = t.indexOf( x, y[i] )
                if index > -1 then t.remove( x, index ) end
            end
            return x
        end
    end,
    __call = function(d, ...)
        for i,v in next, d do
            v(...)
        end
    end
}

local meta2 = {
    __add = meta.__add,
    __sub = meta.__sub,
    __call = function( d, ... )
        local result = arg or {}
        for i,v in next, d do
            result = { v( unpack(result) ) }
        end

        return unpack(result)
    end
}
local function newDelegate( bool )
    local d = {}
    --bool==false, use same arguments for every function
    --bool==true, will pass retrun result to next function
    setmetatable(d, bool and meta2 or meta)
    return d
end
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--
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local function step1( n )
    print("Step1", n, n + 10 )
    return n + 10
end

local function step2( n )
    print("Step2", n, n + 20 )
    return n + 20
end

local function step3( n )
    print("Step3", n, n + 30 )
    return n + 30
end

local d = newDelegate()
local d2 = newDelegate( true )

d = d + { step3, step2 }
d2 = d2 + { step1, step2, step3 }
print("d(0):")
d( 0 )
d = d - step2
print("d = d - step2 ; d(0)")
d( 0 )
print("d2( 100 ):")
d2( 100 )
print("-----------------")
d2 = d2 - step2
print("d2 = d2 - step2 ; d2(100)")
d2( 100 )