Lua编程示例（二）：面向对象、metatable对表进行扩展
counter={
count=0
}
functioncounter.get(self)
returnself.count
end
functioncounter:inc()
self.count=self.count+1
end
print(counter.get(counter))
counter.inc(counter)
print(counter.get(counter))
counter2={
count=4,
get=counter.get,
inc=counter.inc,
}
print(counter2:get())
counter.inc(counter2)
print(counter2.get(counter2))
print()
tb1={"alpha","beta","gamma"}
mt={}
setmetatable(tb1,mt)
print(getmetatable(tb1)==mt)
print()
functionmt.__add(a,b)
localresult=setmetatable({},mt)
fori=1,#ado
table.insert(result,a[i])
end
fori=1,#bdo
table.insert(result,b[i])
end
returnresult
end
tb2={"aaa","bbb","ccc"}
res=tb1+tb2
fori,vinipairs(res)do
print(v)
end
print()
functionmt.__unm(a)
localresult=setmetatable({},mt)
fori=#a,1,-1do
table.insert(result,a[i])
end
returnresult
end
res=-tb1+tb2
fori,vinipairs(res)do
print(v)
end
print()
functionmt.__tostring(a)
localresult="{"
fori,vinipairs(a)do
result=result..""..v
end
result=result.."}"
returnresult
end
print(tb1)
functionmt.__index(tb1,key)
print("thereisno"..key.."inthetable")
returnnil
end
print(tb1["fsy"])
functionmt.__newindex(a,key,v)
if(key=="haha")then
error("Stoplaugh!",2)
else
rawset(a,key,v)
end
end
tb1.haha="heihei"
运行结果：
0
1
4
5
true
alpha
beta
gamma
aaa
bbb
ccc
gamma
beta
alpha
aaa
bbb
ccc
{alphabetagamma}
thereisnofsyinthetable
nil
lua:my_test.lua:166:Stoplaugh!
stacktraceback:
[C]:infunction'error'
my_test.lua:160:infunction<my_test.lua:158>
my_test.lua:166:inmainchunk
[C]:?