实现一个事件观察者

--worldobserver.lua [[DESC:]]
--主题类
local subject = {}
subject.__index = subject

function subject:new()
local newsubject = {}
newsubject.topiclist = {}
newsubject.topicob = {}
setmetatable(newsubject,subject)
return newsubject
end

function subject:register(observer)
for k,ob in pairs(self.topicob) do
if ob ==observer then
return
end
end
table.insert(self.topicob,observer)
return true
end

function subject:unregister(observer)
for k,ob in pairs(self.topicob) do
if ob == observer then
self.topicob[k] = nil
return true
end
end
return false
end

function subject:update(topic,context)
self.topiclist[topic] = context
self:notifyobserver(topic,context)
end

function subject:notifyobserver(topic,context)
for _,ob in pairs(self.topicob) do
--notice observer who concern this topic
if ob.concern[topic] then
ob.recive(topic,context)
end
end
end

--观察者
local observer = {}
observer.__index = observer

function observer:new(concernlist,dealfunc)
local newobserver = {}
newobserver.concern = {}
for _,obtopic in pairs(concernlist) do
newobserver.concern[obtopic] = true
end
newobserver.recive = dealfunc
setmetatable(newobserver,observer)
return newobserver
end

weather = subject:new()
xiaohong = observer:new({"temp","sun","rain"},function (topic,context)
if topic == "temp" then
if context == -1 then
print("xiaohong: I think it's too cold!")
else
print("xiaohong: not bad today!")
end
end

if topic == "sun" then
print("xiaohong: sun is " .. context)
end

if topic == "rain" then
print("xiaohong: rain is " .. context )
end
end)
xiaolv = observer:new({"sun"},function (topic,context)
if context == -1 then
print("xiaolv: Is xiaohong hate cloudy?")
else
print("xiaolv: Sun! I love sun!")
end
end)

xiaolan = observer:new({"temp","rain"},function (topic,context)
if topic == "temp" then
if context == -1 then
print("xiaolan: Is xiaohong hate cold?")
else
print("xiaolan: It's warm today!")
end
end
if topic == "rain" then
if context == -1 then
print("xiaolan: Rain is romantic!")
else
print("xiaolan: It isn't rain today")
end
end
end)

weather:register(xiaohong)
weather:register(xiaolv)
weather:register(xiaolan)
--weather:update("temp",1)
--weather:update("sun",1)
weather:update("rain",1)