(搬运工)基于Lua的State Pattern

Posted on 2012-05-07 13:58 点点滴滴阅读(417) 评论(0) 编辑收藏引用

class.lua实现了在Lua中创建类的模拟，非常方便。class.lua参考自http://lua-users.org/wiki/SimpleLuaClasses

1
-- class.lua 

2
-- Compatible with Lua 5.1 (not 5.0). 

3

4
function class(base, init) 

5
local c = {} -- a new class instance 

6
if not init and type(base) == 'function' then

7
init = base 

8
base = nil

9
elseif type(base) == 'table' then

10
-- our new class is a shallow copy of the base class! 

11
for i,v in pairs(base) do

12
c[i] = v 

13
end

14
c._base = base 

15
end

16
-- the class will be the metatable for all its objects, 

17
-- and they will look up their methods in it. 

18
c.__index = c 

19

20
-- expose a constructor which can be called by <classname>(<args>) 

21
local mt = {} 

22
mt.__call = function(class_tbl, ...) 

23
local obj = {} 

24
setmetatable(obj,c) 

25

26
-- below 2 lines are updated based on the Comments from 'http://lua-users.org/wiki/SimpleLuaClasses' 

27
-- if init then 

28
-- init(obj,...) 

29
if class_tbl.init then

30
class_tbl.init(obj,...) 

31
else

32
-- make sure that any stuff from the base class is initialized! 

33
if base and base.init then

34
base.init(obj, ...) 

35
end

36
end

37
return obj 

38
end

39
c.init = init 

40
c.is_a = function(self, klass) 

41
local m = getmetatable(self) 

42
while m do

43
if m == klass then return true end

44
m = m._base 

45
end

46
return false 

47
end

48
setmetatable(c, mt) 

49
return c 

50
end

State基类，包含三个stub函数，enter()和exit()分别在进入和退出state时被执行，onUpdate()函数将会在state被激活时的每帧被执行。

1
require "class"

2

3
State = class() 

4

5
function State:init( name ) 

6
self.name = name 

7
end

8

9
function State:enter() 

10
end

11

12
function State:onUpdate() 

13
end

14

15
function State:exit() 

16
end

StateMachine类，该类集成了Moai的MOAIThread类。MOAIThread类似于Lua中的coroutine，但是在Moai中被yield的MOAIThread，会在game loop的每帧中被自动resume，见StateMachine:updateState函数，利用此特点，来实现每帧执行State:onUpdate函数。

1
require "State"

2

3
StateMachine = class() 

4

5
function StateMachine:init() 

6
self.currentState = nil

7
self.lastState = nil

8
end

9

10
function StateMachine:run() 

11
if ( self.mainThread == nil ) 

12
then

13
self.mainThread = MOAIThread.new() 

14
self.mainThread:run( self.updateState, self ) 

15
end

16
end

17

18
function StateMachine:stop() 

19
if ( self.mainThread ) 

20
then

21
self.mainThread:stop() 

22
end

23
end

24

25
function StateMachine:setCurrentState( state ) 

26
if ( state and state:is_a( State ) ) 

27
then

28
if ( state == self.currentState ) 

29
then

30
print( "WARNING @ StateMachine::setCurrentState - " .. 

31
"var state [" .. state.name .. "] is the same as current state" ) 

32
return

33
end

34
self.lastState = self.currentState 

35
self.currentState = state 

36
if ( self.lastState ) 

37
then

38
print( "exiting state [" .. self.lastState.name .. "]" ) 

39
self.lastState:exit() 

40
end

41
print( "entering state [" .. self.currentState.name .. "]" ) 

42
self.currentState:enter() 

43
else

44
print( "ERROR @ StateMachine::setCurrentState - " .. 

45
"var [state] is not a class type of State" ) 

46
end

47
end

48

49
function StateMachine:updateState() 

50
while ( true ) 

51
do

52
if ( self.currentState ~= nil ) 

53
then

54
self.currentState:onUpdate() 

55
end

56
coroutine.yield() 

57
end

58
end

如何利用State和StateMachine类的示例，首先定义两个state。
SampleState.lua

1
require "State"

2

3
State1 = class( State ) 

4

5
function State1:init() 

6
State.init( self, "State1" ) 

7
end

8

9
function State1:enter() 

10
self.i = 0 

11
end

12

13
function State1:exit() 

14
self.i = 0 

15
end

16

17
function State1:onUpdate() 

18
print( self.name .. " is updated" ) 

19
self.i = self.i + 1 

20
print( "self.i=" .. self.i ) 

21
if ( self.i == 10 ) 

22
then

23
print( state2 ) 

24
SM:setCurrentState( state2 ) 

25
self.i = 0 

26
end

27
end

28

29
----------------------- 

30

31
State2 = class( State ) 

32

33
function State2:init() 

34
State.init( self, "State2" ) 

35
end

36

37
function State2:onUpdate() 

38
print( "State2 is updated" ) 

39
end

test.lua

1
require "StateMachine"

2
require "SampleState"

3

4
SM = StateMachine() 

5
SM:run() 

6
state1 = State1() 

7
state2 = State2() 

8
SM:setCurrentState( state1 )

点点滴滴

(搬运工)基于Lua的State Pattern

日历

公告

留言簿(9)

随笔分类(268)

随笔档案(311)

相册

搜索

积分与排名

最新评论