[CoronaSDK/Lua] Function Delegate

FuncDelegate.lua

-------------------------------------
-- function delegate
-- Author: Erin Lin
-- www.erinylin.com
-- 簡易模擬 C# delegate
-- licensed under the MIT license.
-- 2015, 02
-------------------------------------
--[[
    Usage1:

    local function step1()
        print("Step1")
    end

    local function step2()
        print("Step2")
    end

    local function step3()
        print("Step3")
    end

    local delegate = require("FuncDelegate").new()
    delegate:insert( step1 ):insert( step2 ):insert( step3 )
    -- Output:
    -- Step1
    -- Step2
    -- Step3

    Usage 2:

    local function step1( n )
        print("Step1", n )
        return n + 10
    end

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

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

    local delegate = require("FuncDelegate").new()
    delegate:insert( step1 ):insert( step2 ):insert( step3 )
    print("delegate:run( 0 ) =", delegate:run( 0 ) )
    print("delegate:runWithSameArgs( 0 ) =", delegate:runWithSameArgs( 0 ) )
    -- Output:
    -- Step1 0
    -- Step2 10
    -- Step3 30
    -- delegate:run( 0 ) = 60

    -- Step1 0
    -- Step2 0
    -- Step3 0
    -- delegate:runWithSameArgs( 0 ) = 10
--]]

local M = {
    _pool = {}
}

local M_mt = {__index=M}

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
}

function M:insert( element )
    assert( type(element)=="function", "argument must be a type of function")
    local index = t.indexOf( self._pool, element )
    if index<0 then
        t.insert( self._pool, element )
    end
    return self
end

function M:remove( element )
    local index = t.indexOf( self._pool, element )
    if index > -1 then
        t.remove( self._pool, index )
    end
    return self
end
-- will pass retrun result to next function
-- 會將前一個函式的回傳值傳到下一個函式，但是如果都是無回傳，用 run or runWithSame 都無所謂
function M:run( ... )
    local result = arg or {}
    for i=1,#self._pool do
       result = { self._pool[i](unpack( result )) }
    end
    return unpack( result )
end
-- use same arguments for every function
-- 全部函式都用一開始的傳入值
function M:runWithSameArgs( ... )
    local params = arg or {}
    local result = {}
    for i=1, #self._pool do
        result = { self._pool[i](unpack( params )) }
    end
    -- only return last function's result
    return unpack(result)
end

function M:clear()
    for i=#self._pool,1,-1 do
        self._pool[i] = nil
    end
end

function M.new()
    local obj = {}
    setmetatable( obj, M_mt )
    obj._pool = {}
    return obj
end

return M