cocos2dx中lua实现继承详解

环境： cocos2dx版本为2.1.4 目标： 游戏中一般有玩家和怪物，他们都有相同的动作状态，如：idle、walk、attack、defense等，我们需要抽象出玩家和怪物的代码实现中中相同的部分 方法： cocos2dx中其实已经提供了类继承的一下工具函数，在sdk中的samples/Lua

环境：

cocos2dx版本为2.1.4

目标：

游戏中一般有玩家和怪物，他们都有相同的动作状态，如：idle、walk、attack、defense等，我们需要抽象出玩家和怪物的代码实现中中相同的部分

方法：

cocos2dx中其实已经提供了类继承的一下工具函数，在sdk中的samples/Lua/TestLua/Resources/luaScript目录下有一个名为“extern.lua”，其中有段代码如下：

--Create an class.
function class(classname, super)
    local superType = type(super)
    local cls
 
    if superType ~= "function" and superType ~= "table" then
        superType = nil
        super = nil
    end
 
    if superType == "function" or (super and super.__ctype == 1) then
        -- inherited from native C++ Object
        cls = {}
 
        if superType == "table" then
            -- copy fields from super
            for k,v in pairs(super) do cls[k] = v end
            cls.__create = super.__create
            cls.super    = super
        else
            cls.__create = super
        end
 
        cls.ctor    = function() end
        cls.__cname = classname
        cls.__ctype = 1
 
        function cls.new(...)
            local instance = cls.__create(...)
            -- copy fields from class to native object
            for k,v in pairs(cls) do instance[k] = v end
            instance.class = cls
            instance:ctor(...)
            return instance
        end
 
    else
        -- inherited from Lua Object
        if super then
            cls = clone(super)
            cls.super = super
        else
            cls = {ctor = function() end}
        end
 
        cls.__cname = classname
        cls.__ctype = 2 -- lua
        cls.__index = cls
 
        function cls.new(...)
            local instance = setmetatable({}, cls)
            instance.class = cls
            instance:ctor(...)
            return instance
        end
    end
 
    return cls
end

函数class的第一个参数就是我们要实现的类的名称，可以不传第二个参数或者给第二参数传一个function或者table。

我们从cocos2dx中的CCSprite继承，根据不同的状态播放不同的动画

实现：

玩家和怪物的基类可如下实现：

require "extern"

Actor = class("Actor", function()
    return CCSprite:create()
end)

Actor.__index = Actor

-- 常量
kActorStateUnkown = 0
kActorStateIdle = 1
kActorStateAttack = 2
kActorStateDefense = 3
kActorStateWalk = 4

-- 属性
Actor._state = kActorStateUnkown
Actor._idle_action = nil
Actor._attack_action = nil
Actor._defense_action = nil
Actor._walk_action = nil

-- 方法
function Actor:idle()
  if self._state ~= kActorStateIdle then
    self:stopAllActions()
    pcall(self:runAction(self._idle_action))
    self._state = kActorStateIdle
  end
end

function Actor:attack()
  if self._state ~= kActorStateAttack then
    self:stopAllActions()
    pcall(self:runAction(self._attack_action))
    self._state = kActorStateAttack
  end
end

function Actor:defense()
  if self._state ~= kActorStateDefense then
    self:stopAllActions()
    pcall(self:runAction(self._defense_action))
    self._state = kActorStateDefense
  end
end

function Actor:walk()
  if self._state ~= kActorStateWalk then
    self:stopAllActions()
    pcall(self:runAction(self._walk_action))
    self._state = kActorStateWalk
  end
end

function Actor:create()
  local actor = Actor.new()
  return actor
end

有了基类后，玩家的的实现可以如下：

1、玩家的数据单例

require "extern"

PlayerData = class("PlayerData")

PlayerData.__index = PlayerData

PlayerData._inited = 0
PlayerData._idle_action = nil
PlayerData._attack_action = nil
PlayerData._defense_action = nil
PlayerData._walk_action = nil

function PlayerData:lazyInit()
  if (self._inited ~= 0) then
    return
  end

  local cache = CCSpriteFrameCache:sharedSpriteFrameCache()
  cache:addSpriteFramesWithFile("pd_sprites.plist")

  local frames = nil
  local frame = nil
  local anim = nil

  -- idle
  frames = CCArray:createWithCapacity(6)
  for i = 0, 5 do
    frame = cache:spriteFrameByName(
        string.format("hero_idle_%02d.png", i))
    frames:addObject(frame)
  end
  anim = CCAnimation:createWithSpriteFrames(frames, 1.0 / 12.0) 
  self._idle_action = CCRepeatForever:create(CCAnimate:create(anim))

  -- attack
  frames = CCArray:createWithCapacity(3)
  for i = 0, 2 do
    frame = cache:spriteFrameByName(
        string.format("hero_attack_00_%02d.png", i))
    frames:addObject(frame)
  end
  anim = CCAnimation:createWithSpriteFrames(frames, 1.0 / 12.0) 
  self._attack_action = CCRepeatForever:create(CCAnimate:create(anim))

  -- defense
  self._defense_action = self._idle_action

  -- walk
  frames = CCArray:createWithCapacity(8)
  for i = 0, 7 do
    frame = cache:spriteFrameByName(
        string.format("hero_walk_%02d.png", i))
    frames:addObject(frame)
  end
  anim = CCAnimation:createWithSpriteFrames(frames, 1.0 / 12.0) 
  self._walk_action = CCRepeatForever:create(CCAnimate:create(anim))

  self._inited = 1
end

function PlayerData:getAllAction()
  self:lazyInit()
  return self._idle_action, self._attack_action, self._defense_action,
    self._walk_action
end

2、玩家类

require "actor"
require "playerdata"

Player = class("Player", function()
    return Actor:create()
end)

Player.__index = Player

function Player:init()
  self._idle_action, self._attack_action, self._defense_action,
    self._walk_action = PlayerData:getAllAction()
end

function Player:create()
  local player = Player.new()
  player:init()
  return player
end