lua语言相关

bool转数字

function MyPackage.bool2number(bool)
    return bool and 1 or 0
end

table相关

function MyPackage.removeValueFromArray(array,value)
    local idx
    for i,v in ipairs(array) do
        if v == value then
            idx = i
            break
        end
    end
    if idx then
        table.remove(array,idx)
    end
end

function MyPackage.hasValueInArray(array,value)
    local hasValue = false
    for i,v in ipairs(array) do
        if v == value then
            hasValue = true
            break
        end
    end
    return hasValue
end

UTF8字符串

cocos2d-x的label默认为UTF8编码，一般场景下主要需要以下两个功能：

• 字符串长度

• 截取子串

原先本渣用cocos2d-x时写了个C++函数来求长度：

long long utf8StringSize(const std::string& str)
{
    char* charArray = new char[str.length() + 1];
    strcpy(charArray,str.c_str());
    char* s = charArray;
    /*-----------------------------------------------------------------------------
     *  References: http://stackoverflow.com/questions/4063146/getting-the-actual-length-of-a-utf-8-encoded-stdstring
     *-----------------------------------------------------------------------------*/
    long long len = 0;
    while (*s) len += (*s++ & 0xc0) != 0x80;
    delete [] charArray;
    return len;
}

cocos2d-x Helper也提供了接口来做字符串截取：

static std::string getSubStringOfUTF8String(const std::string& str,std::string::size_type start,std::string::size_type length);

在lua方面，quickx已经提供string.utf8len来求字符串长度，本渣仿照其实现写了个截取子串的函数：

function MyPackage.utf8str(str,start,num)
    local function utf8CharSize(char)
        local size = 0

        local arr = {0,0xc0,0xe0,0xf0,0xf8,0xfc}
        local size = #arr
        while arr[size] do
            if char >= arr[size] then
                break
            end
            size = size - 1
        end

        return size
    end

    local startIdx = 1
    while start > 1 do
        local char = string.byte(str,startIdx)
        startIdx = startIdx + utf8CharSize(char)
        start = start - 1
    end

    local endIdx = startIdx
    while num > 0 do
        if endIdx > #str then
            endIdx = #str
            break
        end
        local char = string.byte(str,endIdx)
        endIdx = endIdx + utf8CharSize(char)
        num = num - 1
    end

    return str:sub(startIdx,endIdx - 1)
end

不过目前lua5.3已经有UTF8库，可以不用自行造轮子了。另外，关于其他UTF8相关的lua问题可以参考Lua Unicode。

其他Helper Functions

更新view的callbackWrapper

我们经常碰到如下的情景：
游戏向后端请求数据，在拿到数据之后执行某个callback去更新某个view。
这种网络请求通常是异步的，如果所请求的数据回来时相关的view被释放，则执行操作该view的callback会导致问题（例如访问非法内存地址）。
这时候我们可以用tolua.isnull来判断相关的view对象是否被释放。
由于每个这种类型的callback都有必要加上这样的guard code，所以本渣干脆做了如下的接口：

function MyPackage.callbackWrapper(views,callback)
    return function(...)
        for _,view in pairs(views) do
            if tolua.isnull(view) then
                return
            end
        end
        if callback ~= nil then
            callback(...)
        end
    end
end

拿到一个node九个端点的坐标

--[[--
get the nine positions of a node (the following variables are defined in display.lua of quickx):
display.CENTER
display.LEFT_TOP
display.CENTER_TOP
display.RIGHT_TOP
display.CENTER_LEFT
display.CENTER_RIGHT
display.BOTTOM_LEFT
display.BOTTOM_RIGHT
display.BOTTOM_CENTER
]]
function MyPackage.getPositionOfNode(node,alignType)
    if not node or tolua.isnull(node) then
        return
    end

    local size = node:getContentSize()
    if size.width == 0 and size.height == 0 then
        size = node:getCascadeBoundingBox()
    end

    local pos = cc.p(node:getPosition())
    local anchorPoint = cc.p(node:getAnchorPoint())

    if alignType == display.LEFT_TOP or
        alignType == display.LEFT_CENTER or
        alignType == display.LEFT_BOTTOM then
        pos.x = pos.x - size.width * anchorPoint.x
    elseif alignType == display.CENTER_TOP or
        alignType == display.CENTER or
        alignType == display.CENTER_BOTTOM then
        pos.x = pos.x - size.width * anchorPoint.x + size.width * 0.5
    elseif alignType == display.RIGHT_TOP or
        alignType == display.RIGHT_CENTER or
        alignType == display.RIGHT_BOTTOM then
        pos.x = pos.x - size.width * anchorPoint.x + size.width
    end

    if alignType == display.BOTTOM_LEFT or
        alignType == display.BOTTOM_CENTER or
        alignType == display.BOTTOM_RIGHT then
        pos.y = pos.y - size.height * anchorPoint.y
    elseif alignType == display.CENTER_LEFT or
        alignType == display.CENTER or
        alignType == display.CENTER_RIGHT then
        pos.y = pos.y - size.height * anchorPoint.y + size.height * 0.5
    elseif alignType == display.TOP_LEFT or
        alignType == display.TOP_CENTER or
        alignType == display.TOP_RIGHT then
        pos.y = pos.y - size.height * anchorPoint.y + size.height
    end

    return pos
end

在某个container中加入sprite，可指定根据container大小进行缩放及对齐方式

function MyPackage.displaySpriteOnContainer(sprite,container,scaleToFit,alignType)
    if tolua.isnull(container) then
        return
    end

    -- default settings
    local scaleToFit = (scaleToFit ~= false)
    local alignType = alignType or display.CENTER

    if not tolua.isnull(sprite) then
        local originSize = sprite:getContentSize()
        if originSize.width == 0 or originSize.height == 0 then
            originSize = sprite:getCascadeBoundingBox()
        end

        local targetSize = container:getContentSize()
        if targetSize.width == 0 or targetSize.height == 0 then
            targetSize = container:getCascadeBoundingBox()
        end

        if scaleToFit then
            sprite:setScale(targetSize.width / originSize.width,targetSize.height / originSize.height)
        end

        -- NOTE: ignore container's anchor point
        local pos = MyPackage.getPositionOfNode(container,alignType)
        local leftBottomPos = MyPackage.getPositionOfNode(container,display.LEFT_BOTTOM)
        local posX = pos.x - leftBottomPos.x
        local posY = pos.y - leftBottomPos.y
        display.align(sprite,alignType,posX,posY)
        container:addChild(sprite)
    end
end